Fire Service Manual Volume 1. Fire Service Technology, Equipment and Media (1998) - part 4

 

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Fire Service Manual Volume 1. Fire Service Technology, Equipment and Media (1998) - part 4

 

 

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10.3.11 Personal Equipment
10.3.12 Methods of using Personal
Radios
'Personal' equipment is small enough to be carried
in the hand or pocket, or in a suitable lightweight
Personal set communication can be organised in a
body-harness. Its small size means miniature con-
number of different ways to meet various opera-
struction techniques which create problem in the
tional needs which, in broad terms, break down
receiver, but which do create difficulties in the
into the following categories:
transmitter. The battery size is severely limited and
those two factors restrict the transmitter power to a
Direct person-to-person communication on
fraction of what is obtainable from 'transportable'
an exclusive single frequency channel over
equipment (normally approximately 1 watt in the
very short distances e.g., between individuals
majority of equipment). This, coupled with the
at an incident, or when carrying out dry riser
restricted aerial dimensions and efficiency, limits
tests - or other duties - in high rise buildings.
the range of the transmitter section. The receiver
performance will be comparable to that of a trans-
Similar communication but in which one of
portable under similar conditions.
the units is mounted in a vehicle.
Personal equipment can operate in either the VHF
Two-frequency communication between per-
or the UHF band, but VHF equipment, other than
sonal sets via a vehicle-mounted or portable
in the single frequency mode, would normally be
VHF repeater.
expected to transmit into the main scheme hill-top
sites. VHF equipment is perfectly satisfactory on a
Two-frequency communication between per-
single frequency basis to other personal, trans-
sonal sets and the brigade control room via a
portable or mobile units over short ranges, but in
vehicle-mounted UHF/VHF repeater.
general UHF offers better performance for person-
al radios. The use of FM offers advantages for per-
Single Frequency Operation
sonal radios, if only because it permits greater
transmitter power to be obtained from a given size
Figure
10.13 (1) involves personal sets only and,
of battery, and all UHF personal radios used with-
although only two are shown, any number can be
in the fire service operate on FM.
used on an 'all-hear-all' basis subject to the limita-
Figure 10.13
(1) Single-frequency
personal set usage.
(2) Single-frequency
personal sets with
control set.
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Figure 10.14 Double
frequency personal set
Control
usage with control set
Set
on talk-through.
Personal Set
'Talk-through'
Personal Set
control point equipment is well sited and has an
tions of range imposed by location and environ-
efficient aerial, this arrangement has the advantage
ment. With more than two units it may well be the
that working range between the control point and
case that unit 'B ' can communicate perfectly with
individual personal set users is greatly improved.
both unit 'A' and unit C whereas units 'A' and 'C
However, with single-frequency working, effec-
cannot communicate directly at all.
tive range between individuals depends upon them
When switched to a single frequency channel a
being within direct range of each other, this
personal radio transmits and receives on the same
arrangement will not improve person-to-person
radio frequency and, when used without the aid of
communication. The control set operator could,
any control station equipment, has the following
however, personally relay messages from one per-
limitations:
sonal set user to another where they are not within
direct working range.
(i)
Its effective direct range between individuals
is seriously affected by the screening phe-
It should be noted that when a user is transmitting,
nomena. Therefore, the general range and
they will not be able to hear calls from other users.
performance must be expected to vary con-
stantly as the individuals move about.
Two-Frequency UHF Personal Set Channels
(ii) It is not possible to forecast accurately what
UHF multi-channel personal equipment with three
the performance will be in any particular
or more channels has been adopted by most fire
building or other environment, and it does
brigades for fireground purposes. Four of the six
not follow that because good results are
channels utilise single-frequency working and two
obtained in one building, similar results will
utilise a two-frequency channel. The two-frequen-
necessarily be achieved in a nearby and
cy channels cannot be used for direct person-to-
similar building.
person communications without a suitable control
set. Figure 10.14 illustrates the arrangement which
To summarise, performance can be expected to
is adopted when using two-frequency personal set
vary from one extreme, where screening is severe
channels. All outgoing transmissions from the
and when communication even over very short
'control' set are on one frequency
(f.a.) and all
distances is unreliable, to the other extreme where
incoming transmission from 'personal set' users
there is little or no screening, good communication
are on another frequency, (f.b.). Therefore, since
over several miles is not uncommon.
all 'personal set' receivers' two-frequency chan-
nels are tuned to frequency (f.a.) they cannot hear
Figure 10.13 (2) illustrates the use of a control set
transmissions direct from other 'personal set'
using single-frequency equipment. Provided the
transmitters, which are tuned to frequency (f.b.).
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Nevertheless, this arrangement has advantages
Normally there is no operational requirement for
over single-frequency working especially when
permanently engineered Fire Service 'personal set'
there is a need to increase working ranges between
schemes similar to those which are an operational
individuals. This is achieved by a "talkthrough"
necessity for the police. The normal Fire Service
facility on the 'control set' for use when it is nec-
requirement is the need for completely portable short
essary to automatically re-transmit on the outgoing
range systems which can be set up and brought into
frequency (f.a.) all incoming signals received from
use at very short notice anywhere at incidents.
'personal set' transmitters on frequency
(f.b.).
When the 'talk-through' facility is off, the 'control
At specific locations fixed UHF base stations
set' operator will hear and be able to communicate
(repeaters) may be authorised by RFCPU for use
with all 'personal set' users within range, but 'per-
in road tunnels or airports, etc. However such use
sonal set' users will not be able to hear each other.
is strictly limited according to the stated opera-
tional requirement when the licence was granted.
There is no reason why the 'control set' should not
be switched to 'talk-through' on the two-frequency
10.3.13 Composite Units
channel and left unattended when the requirement
is for good communication between 'personal set'
A vehicle with a mobile UHF control unit will
users. All six channels may be used simultaneously
usually have a VHF mobile radio fitted, and an
at the same incident without mutual interference.
operator in the vehicle can then communicate
with both the 'personal set' users and the
The 'talk-through' facility provides considerably
brigade control room. An added facility is an
enhanced range between 'personal sets' above that
interface, usually in the form of a combined
obtainable with single-frequency working because
UHF/VHF control unit which connects to both
of the greater performance of the vehicle-mounted
transmitter/receiver units.
or 'portable set' and its aerials.
The equipment collectively is now known as a
It is customary to designate the direction from con-
'VHF/UHF Repeater Unit", and it can be used in
trol as 'outgoing' and the direction to control as
three distinct ways:
'incoming'. The equipment thus has a true control
function, exactly the same as that which the
(1) Local control of a two-frequency UHF net-
brigade control room has over the main VHF
work and VHF communication with brigade
scheme, hence the operator at the fire ground can
HQ, but not simultaneously because although
control the miniature UHF scheme in just the same
the repeater control unit has two loud-speak-
way. Vehicle-mounted sets are normally fully
ers, it has only one handset which is switched
duplex, usually with separate transmit and receive
to VHF or UHF as required.
aerials although it is possible to use a single aerial
with an additional unit, known as a 'duplexer'
(2) Talk-through between 'personal set' users
which enables the transmitter and receiver to oper-
with the vehicle set unattended or, with the
ate independently and simultaneously with a single
vehicle operator solely involved with VHF
aerial.
communication to the Brigade HQ.
The conditions of licence, under which frequen-
(3) With the vehicle control unit switched to
cies are allocated and radio communications
'repeat', all signals received on VHF are re-
authorised, restrict the use of Fire Service person-
transmitted on UHF and vice versa so that the
al sets to low power, short range communications.
•personal sets' all hear brigade HQ just like a
In consequence, the setting up of fixed base sta-
mobile or transportable, and individual per-
tions on 'personal set' frequencies, VHF or UHF,
sonal set users can speak directly back to
to give greater working ranges
(for example,
Brigade HQ.
throughout a town or city) is not permitted because
of the risk of causing interference to other brigades
In (3) above the vehicle will usually be unattended
in neighbouring areas.
or at least without a designated operator, and it can
Communications and Mobilising
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be arranged that when on 'repeat' the two loud-
10.3.16 B.A. Radio Communications
speakers are switched off to prevent unauthorised
Interfaces
listening-in'. One minor drawback of the repeater
is that personal sets are not able to directly com-
Fire Service Circular 3/75 recommended that all
municate with each other; the vehicle VHF radio is
future purchases of B.A. should comply with BS
'simplex' and its receiver switches off when trans-
4667 and should be covered by a Certificate of
mitting. When a personal radio transmits, the UHF
Assurance (C. of A.) issued in accordance with the
receiver in the vehicle switches on the VHF trans-
Joint Testing memorandum.
mitter back to control, and the VHF receiver is
switched off. The UHF transmitter to the personal
From 1 January 1990, under COSHH Regulations,
sets therefore also switches off and they appear to
BA equipment has to be suitable for its intended
go 'dead'.
use and approved by the HSE. It will be certificat-
ed under HSE Testing Memorandum No. 3 (TM3).
10.3.14 Personal Hand-Held Radio Sets
New CEN standards will apply when they become
available.
A limited number of frequencies are specially
allocated on a national basis for use by fire
Any fitting must have the prior approval of the
brigades, some in the VHF band and others in the
manufacturer who, as the holder of the C.of A., can
UHF band. Fireground communication is
ensure that, if any amendment to the C. of A. is
presently carried out using the UHF band of fre-
required, it will be HSE approved.
quencies. Personal hand-held equipment is nor-
mally designed to accommodate a minimum of 3
10.3.17 Disadvantages of use of radio
channels. However, with the allocation of 6 UK-
with B.A.
wide Fire Service UHF frequencies for their
exclusive use and possible additional channels
Firefighters should particularly bear in mind that
for other purposes, there is a need for synthesised
there are disadvantages to the use of radios with BA.
multi-channel equipment which, for a number of
years, will be used in addition to existing 3-chan-
Radio signal penetration in some types of
nel equipment.
buildings can be limited.
10.3.15 Intrinsically Safe Personal
Some atmospheres are so potentially haz-
Radios
ardous that only communications equipment
with the highest standard of explosion protec-
Ordinary personal radio equipment is capable, in
tion should be used.
flammable atmospheres, of causing explosions or
fire. Intrinsically safe equipment is designed,
Radio systems can operate explosive devices
when correctly used and maintained, to operate
designed to be operated remotely.
safely even if it develops a fault. Personal radios
certified to BS 5501 Part 7 or European Standard
Radio transmitters may interfere with build-
EN50
020 for Category ib. Group IIC and
ing control systems.
Temperature Class T4, provide the minimum stan-
dard that should be used. The harmonised stan-
10.3.18 User Discipline
dard CENELEC Eex ib IIC T4, is often referred to
and equally valid.
(See DCOL 8/95 Item A, in
The increased use of BA fireground radio general-
Scotland DFM 6/1995 item A.)
ly, requires good radio discipline. A very compli-
cated radio call-sign system could interfere with
Each user should satisfy themselves that this
operational flexibility and command at an incident
equipment is suitable for use at incidents in their
and, therefore, self-evident call-signs are recom-
area. If in any doubt about the suitability or use
mended. Call-signs, however, should be such that
of their equipment then H.M. Fire Service
the brigade can be identified from them, especial-
Inspectorate should be consulted.
ly in a multi-brigade incident.
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The possibility of cross-incident and inter-brigade
10.3.19 Security
interference from the use of over-powerful trans-
mitters should be guarded against.
Modern hand-held radio equipment is of signifi-
cant financial value and can also be of great value
The transmit/receive ratio of the use of radio
to others, outside the service, if used unlawfully.
should always be considered. Transmissions
Accordingly, radio equipment should never be left
should, wherever possible, be of short duration
unattended on appliances unless it is suitably
with an adequate pause to allow other users of the
secured against theft.
frequency, with perhaps a higher priority message,
to transmit.
Handheld or portable radios should never be left
exposed to public view in unattended cars, even if
It is not possible for two UHF repeaters or mobile
the car is secured.
base stations on the same channel to operate simul-
taneously within range of each other. Therefore, it
Arrangements for securing handheld radios on
is essential that, where this happens, the
appliances will vary between brigades. Suitable
repeater/base station in the least advantageous
arrangements could, for example, include a locked
location is switched off.
container secured in the appliance from which the
radio can be taken when required.
Regulatory approval must be obtained from
RFCPU before specifying the installation of fixed
10.3.20 Care Of Hand-Held Radio
UHF equipment which will be left permanently
Equipment
switched on.
The initial purchase of any handheld radio equip-
Radio communications could be required to oper-
ment should include suitable protective carrying
ate deep within an underground railway system,
cases. The design chosen must take account of
railway tunnels, building sub-basements and other
local requirements. Even if the equipment pro-
complex constructions. The potential of deploy-
cured is water-resistant the protective case should
ing 'throw-out' and 'inbuilt' leaky-feeder sys-
be designed so that it minimises the chances of the
tems should be considered even during the
battery terminals/connections, aerials or controls
early stages of an incident.
coming into contact with water or spray. This is
particularly important where the design of the
A great deal of research is currently underway to
radio equipment is such that water can collect near
improve underground radio communications.
any of these fittings.
Figure 10.15 Trunking
concept.
Communications and Mobilising
97

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Virtually any electrical or electronic equipment
basestation. A mobile radio will be constantly
will fail if subjected continually to heat in excess
"speaking" to its local basestation via a control
of that in which it was designed to operate.
channel.
Battery compartments of radio equipment should
When the mobile wishes to send a message the
be kept closed (and locked in the case of intrinsi-
control channel will allocate a speech channel
cally safe equipment) except when batteries are
dynamically, and communications will be avail-
being changed. Batteries of explosion protected
able. At the end of the transmission, and at each
equipment must never be changed within the haz-
subsequent transmission different channels may be
ard area.
used. Once the transaction is complete these chan-
nels would then be available for other users.
Radio equipment should be carried in such a way
that it cannot easily be dropped, strike another
Unlike cellular systems which are generally
solid object, become exposed to water, water
designed to be a one to one service, 'trunked'
spray, corrosive chemicals, or be subject to any
radio schemes can set up user groups in which
unnecessary or abnormal mechanical stress.
multiple users will be able to talk.
Radios should not be carried in containers with
'Trunked' radios permit 'roaming' throughout the
other metallic objects which could make accidental
area required, with handover between radio cells
connection with battery charging or other external
as a mobile passes from one base station area to
radio connections. When external equipment not
another. The mobile receiver will be constantly
connected to any socket, a protective cover should
hunting for a control channel during this exercise.
always be in place over the exposed connectors.
Once a signalling channel is identified the sig-
nalling information is examined and checked by
10.4 Trunked mobile radio systems
the mobile, and if validated, locks the mobile to
this channel. This process happens automatically,
The growth in mobile radio systems over the years,
and transparently to the user.
and the subsequent demand for frequencies has
placed an ever increasing load on the spectrum
In the UK, the MPT 1327 signalling standard is
managers. The concept of 'Trunked' radio schemes
used to facilitate analogue 'trunked' private mobile
goes far in addressing this problem.
radio services in "Band III"
(174-225MHz)
although there is no reason why 'trunked' systems
'Trunking' makes greater use of the available
could not operate in different frequency bands.
channels, but leaves users less aware of the con-
gestion on that channel. Users share a pool of
Future development in trunked systems is current-
channels and are only allocated a channel when
ly being addressed by ETSI under the remit of the
they need to make a call. In practice not all users
Trans European Trunked RAdio project (TETRA)
wish to make a call at the same time, and 'trunk-
which will be a digital TDMA product, with an
ing' theory is based on the probability that there
effective bandwidth per voice channel of
will be free channel when required.
6.25KHz, giving four time slots possible within
the 25KHz bandwidth.
The telephone networks have been using 'trunking'
theory for a great many years, but it has only recent-
TETRA will operate for the Emergency Services
ly become economically possible in radio systems
in the band 380-400MHz, and commercially by
with the advent of microprocessor circuitry.
PAMR service providers in 410-430MHz.
Fundamentally, 'trunked' radio systems are engi-
neered in a similar way to cellular telephony sys-
tems, with coverage being modelled in polygon
shaped cells, although it is of course possible that
area coverage is satisfied by a single trunked
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Communications
and Mobilising
Chapter 11 - Radio Alerting System
Currently Brigades use alerting systems to the
facilities it must provide. It will normally have a
Home Office MG4 specification. This forms the
number of communication links, known as 'bear-
final link in the overall mobilising system. The
ers', between Control and the stations and will use
simple schematic below indicates the system ele-
these on the basis of laid down preference and
ments involved.
availability. The types of 'bearer' available to such
systems can change as technology makes them
Mobilising and Communications components of
available and cost effective.
the overall system are dealt with in detail else-
where in this publication. But in the interest of
The station end GD92 is similar but on a smaller
understanding the Alerter system itself a brief out-
scale and serves to interpret incoming instructions
line may be of help.
and operate printers, sounders, lights, doors, appli-
ance bay indicators, etc. In the case of stations
The Mobilising system contains a large amount of
with a retained element instructions from the
detail covering the whole of the Brigade and this is
GD92 unit are passed to the Alerter using the
available to Fire Control Officers when assessing
MG4 protocol.
the operational needs of any particular incident.
Having determined a station or stations to be
11.1
Alerter - General Description
turned out, the detail concerning the incident loca-
tion, the appliances to attend and, if Wholetime,
The requirements of an Alerter system have not
the operation of sounders or, if Retained, the oper-
changed in essence since radio alerting was intro-
ation of alerters, is passed to the Communications
duced. The fundamental need is still to call a
Processor.
retained crew to a station in the case of an incident
or to send a test call to the alerters. What has
The Communications Processor makes use of a
changed is the means and the method of operation
further Home Office Protocol called GD92 which
resulting in greater detail concerning a calls
specifies the way the processor works and the
progress being available at Control.
Figure
11.1 Radio alert-
ing system to the Home
Office MG4 specifica-
tion.{Graphic:Muliitime)
Communications and Mobilising
99

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It is not always the case that an MG4 alerter is
installed at the same time as the Communications
system is upgraded to GD92. In general, older
Mobs/Comms systems presented simple relay con-
tact closures to the Alerter and expected a simple
relay contact closure in return to indicate a suc-
cessful or failed call. MG4 systems have to be able
to operate in this mode leaving the more advanced
MG4 signalling protocol to be implemented at a
later date. This gives a Brigade the flexibility to
upgrade the overall system on a staged basis.
There are basically two component parts to the
system, an encoder and a transmitter. The encoder
generates the call required and the transmitter
sends it to the alerters. It was common practice
with the previous alerter bays to use two transmit-
ters in a main and standby configuration. This has
all but disappeared with the new MG4 alerter sys-
tems on the grounds that modern transmitters are
far more reliable, but the facility is still available
giving Brigades the opportunity to take financial
advantage of the improved technology and still use
dual bay at certain locations if operational needs
dictate.
Standby power is required to cover for the eventu-
ality of mains supply failure and normally this
Figure
11.2
MG4 Alerter Transmitter combined with a
would take the form of batteries designed to give
GD/92 compliant 'Station end' mobilising terminal.
the Brigades stated period of operation. However,
various options are available and a choice depends
on the period of backup and whether or not other
devices share the backup source, for example, the
Generates required team fire or test call using
GD92 Comms unit. The charging of such batteries
POCSAG paging protocol. (See Alerters) Up
would be by stand alone equipment or perhaps via
to 3 teams and the combinations of such are
one of the units already part of the system. This is
catered for.
dependant in part on individual suppliers and their
particular approach. Although there is flexibility in
Generate paging calls with alpha numeric
the type of power supply that can be provided, and
messaging if required for individual calls.
Brigades may request backup periods less than the
MG4 recommendation, suppliers must be in a
Control the sending of calls via the transmit-
position to achieve the 24 hours if requested.
ter and the monitoring of transmitter parame-
ters during calls. (See Transmitter.)
11.2 Encoder
Record the operation of team 'off air' moni-
This component of the Alerter carries out the fol
tor receivers to determine the transmission of
lowing basic functions:
correct call data.
Provides two way communication, using
Assemble the monitored transmitter parame-
MG4 protocol, with the station GD92
ters and the 'off air' receiver status and pro-
Comms equipment.
duce a message indicating a successful or
100

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failed call and send this to the station GD92
A separate frequency allocated to Emergency
Comms unit for onward transmission to con-
Services is often used to provide wide area
trol. If the call is a failure the type of failure
officer paging and on a few occasions has
is also returned.
been used for mobilising purposes. This fre-
quency is 153.05Mhz
Provide a considerable degree of configuration
in order to be able to replace a faulty encoder
11.4
Alerters
at a station with the minimum of delay.
MG4 calls for the use of alerters working to the
Where stations may overlap from the point of
POCSAG format which are produced by virtually
alerting coverage provision is made for cop-
all manufacturers, and uses a
7 digit numeric
ing with simultaneous mobilisation of the two
address or Ric (Receiver identity code) code.
stations.
The Home Office instituted a numbering scheme
It should be noted that although individual manu-
whereby the last three digits are fixed for each
factures have to comply with the requirements of
Brigade. The POCSAG code allows the first four
the MG4 specification they are not restricted from
digits to range from ()()()() to 1999, a total of 2000
providing additional features, either, of their own
codes per Brigade. In the event of a Brigade
idea or at the request of Brigades, subject to these
requiring more Ric codes, if for instance multi-Ric
not compromising the prime requirements. As
code alerters are used for officer paging, then these
these vary from manufacturer to manufacturer it is
are available on application to the Home Office.
not intended to include these in this document.
Two Ric codes are normally required for
Firefighters alerters but versions with 4 codes are
11.3
Transmitter
available.
The transmitter performs the following basic
Alerters need to be robust and have protection
functions:
against ingress of moisture and dust. POCSAG
pager design is driven by the large area wide pag-
As the paging code specified in MG4 is
ing market demands of companies such as BT and
POCSAG (Post Office Code Standardisation
Vodapage together with other international service
Advisory Group) this requires the transmitter
providers. Final design is, therefore, a compromise
to use FSK modulation. The POCSAG code
between design requirements, ready availability,
is referred to in a little more detail under
and competitive pricing. This results in low cost
Receivers.
units which are often cheaper to replace than
repair.
MG4 requires that a minimum of two trans-
mitter parameters be monitored during a call
Firefighters alerters are normally of the 'tone only'
namely forward power and reverse power.
type although some have limited display options to
highlight Fire or Test calls. A flashing LED oper-
The transmitter must be capable of 25 watts
ates on receipt of a call. The use of rechargeable
output with the ability to set alarm trigger
batteries has virtually disappeared although still
levels. As a guide a level of 12 watts (3 db
available. A limited need for intrinsically safe
down) would set the alarm. The reverse
alerters exists, more from the point of view of
power alarm indicates the efficiency of the
equipping Firefighters with such units because of
aerial and would normally trigger at what is
the hazardous areas in which they normally work
termed a 'voltage standing wave ratio' of 2:1
rather than operational reasons. A vibrate option is
or approximately 0% reduced power trans-
available where the normal workplace is subject to
mitted.
high noise levels.
The allocated frequency for Firefighters alert-
The Alerter is required to sound for a minimum of
ing is 147.8Mhz and used throughout the UK.
30 seconds. POCSAG pagers vary in the period of
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Figure 11.3 Alerter.
(Photo:
Multitone)
Attachment
lor lanyard
Beeper
output
Removable
clip
Battery AA
Corporate label area
Call source indicators
On/cancel/
and pager status display
memory recall
Lamp alert
Recessed
off button
Mute mode/delete
Actual size
message button
call generated by receipt of a single call from an
MG4 unit and multiple calls are often used to
achieve the overall required alerting period. This
has the advantage of increasing the chance of
receiving a call as say four calls separated by
12
seconds improve the chances of receiving at least
one good call in areas of weak coverage. Alerters
are equipped with a call cancel button.
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Communications
and Mobilising
Chapter 12 - Mobile Data
12.1 What is Data?
Data transmission capabilities and speeds (rates)
are dependant largely on bandwidth. The band-
In data communications, information is transmit-
width and, hence, capacity, has risen over the years
ted in the form of characters, namely letters, fig-
and hence typical data rates now are around 9600
ures, and symbols. The information is represented
bits per second (bps), and with developing tech-
by binary signals, which are characterised by dif-
nology and compression techniques are expected
ferent states. When considered electrically, these
to rise in the next few years.
signals correspond to, for example, tone ON, and
tone OFF.
Data can be sent both to and from vehicles and
used to supplement information held onboard. The
In digital message transmission over radio circuits,
development of personal computers
(PCs) and
associated software/hardware now allow more
the signal elements of the characters are transmit-
data to be stored onboard vehicles.
ted in turn (serially). Figure
12.1 shows the rela-
tionship between DC keying and VF keying.
12.2 History
The Fire Service has been using Data at incidents
for many years in various formats. 'Data' can be
Resource Availability Status (RAS)
interpreted as telemetry, resource updates, risk
information, and can be deployed as direct links to
The use of mobile data in the Fire Service began in
command and control systems.
the late
1970's when Resource Availability Status
Figure 12.1
Relationship between
DC Keying and VF
Keying.
Communications and Mobilising
103

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Figure 12.2 Typical
Control Operator PC
data transmission
Mobile Printer and Keyboard
arrangement.
Base
Mobile
(RAS) was incorporated into some existing radio
Control personnel action and requiring the Control
systems. The first systems operated at
100 baud
Room staff to change working procedures.
and were literally one way only with the acknowl-
edgement being a single tone. Further develop-
Figure 12.2 above shows a typical data transmis-
ment enabled these systems to operate at 300 baud
sion system. The Dispatcher computer interrogates
with two way communications.
the mobile to establish contact and on receipt of an
acknowledgement, sends the data as a burst trans-
All systems operated over the speech radio net-
mission. The mobile is able to display and/or print
work. One of the major problems associated with
out the received message. The process can also
this shared voice/data radio channel was that data
work in reverse, with the mobile initiating the call.
tones would block speech traffic using the radio
channel. This had the effect of data being received
12.3 Current Technology
but speech having to be re-transmitted.
The term 'mobile data' encompasses data sent
Mobile Data
when an appliance is mobilised, available en route
to an incident, or available at an incident.
Depending upon the level of traffic, it is some-
Requirements for the provision of data vary from
times better to provided a radio channel specifical-
brigade to brigade leading to a multiplicity of sys-
ly for mobile data. This allows a number of differ-
tem configuration. The main elements of these
ent types of messages to be passed. The first sys-
vehicle mounted systems are communications
tems went live in
1989 providing a series of ser-
processors, visual displays, printers, keyboards,
vices to the incident. For example:
radio modems, etc.
Mobilising messages (C&C to mobile).
12.4 Radio Communications
Administrative messages (C&C to Mobile).
Various options are available for the transmission
of data between mobiles, or from mobiles and/or
RAS messages both directions.
fixed locations.
Access to Management Information Systems.
Existing Brigade Radio Schemes - It is possible
to transmit data over existing analogue radio
Access to Chemdata central information.
schemes, in fact some brigades use this bearer as
part of their mobilising arrangements. Typical
Incident messages (mobile to C&C).
transmission rates are
1200bps Frequency Fast
Shift Keying (FFSK).
This was the first time it was possible for mobile
information to be directly input into C&C systems
GSM Cellular Telephone - The Global Systems
(RAS had been possible earlier) without any Fire
for Mobile Communications
(GSM) networks
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Figure 12 3 Data
infrastructure.
(Graphic: Simoco)
Data Infrastructure
Figure 12.3 shows a typical data system infrastructure developed for use by
UK Fire Services. Such a system is able to make use of the Fire Station mobil-
ising system that already forms part of the Command and Control facility at
any Fire Service Communications Control Centre. The mobilising system is
connected to a Data System Controller whose purpose is to control the opera-
tion of the radio data system via the Terminal Server. One function of The Data
System Controller is to transparently convert data into a form suitable for
transmission to the hill top site Radio Modems. The Terminal Server distributes
data to and collects data from the Radio Modems. 'Best hill-top site' informa-
tion is stored and continually updated for all mobiles and the appropriate site
used for any communication with a mobile.
It is possible to send general text messages between Control and mobiles as
well as status messages from mobiles to Control.
incorporate both voice and data modes of opera-
12.5 Data on Vehicles
tion. These networks consist of individual radio
base stations that communicate with the users,
The data available on mobile resources is as
each base station forming a cell. In the data mode
diverse as that held in the office environment.
the system offers a circuit switched, end to end
Individual brigade requirements vary from provid-
communications service and, at present, transmis-
ing limited information held on mobile computers,
sion speeds of up to 9.6K bits per second.
to being able to access personnel records, building
plans, status messaging, global positioning, updat-
Packet Radio Service - There are several commer-
ing the central mobilising system, receiving
cial packet radio data networks. These networks
turnout information and chemical and risk data.
deliver data in the form of bursts or packets. Each
packet contains address information, information
The data available must be current for it to be of
data and some form of error correction.
value. The provision of many geographically scat-
Communications and Mobilising
105

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Figure 12.4 In Cab
Equipment.
Touch-screen
(Graphic: Simoco)
display
Mobile data
processor / PC
Data radio
Keyboard
Printer
Voice radio
In Cab Equipment
Figure 12.4 shows the typical vehicle installation in a Fire Appliance. This
comprises two separate mobile radios, including a Voice Radio which can be
used for voice transmissions at any time and a separate Data Radio operating
on its own radio channel.
The Data Radio, which would incorporate a modem, would be used to pass
status information, various data, and free text information from a Mobile Data
Terminal (MDT) which comprised an in-vehicle PC, Touchscreen Display,
Printer and Keyboard. The PC might be equipped with large capacity hard
drive memory which can hold map data, chemical data, risk files etc., which
can be triggered by the incoming data to give information specific to the
incident. The Touchscreen gives the mobile operator the facility of manually
accessing data, maps etc. or of inputting status or text messages, as required.
The printer makes it possible to produce hard copy of diplaxed data, while the
keyboard max be used for the inputting of text or for maintenance access.
tered mobile data terminals leads to difficulties in
or wire connection to each data terminal when the
maintaining the data, especially if a large percent-
vehicle is in the fire station.
age is held on the terminal. It is essential that a
robust and effective system is established so that
12.6 Typical Data Requirements
updating the stored information is carried out on
all the terminals within a minimum period of time
The following data packages are available for use
on mobile processors, whether held on the mobile,
Part of this process should include an audit trail so
retrieved from a central source or a combination of
that it is possible at a later stage to verify when and
both. Software licensing issues, along with other
who amended any of the data files. Various meth-
factors, may influence whether data is held cen-
ods have been adopted to carry out this procedure
trally or dispersed amongst the mobile terminals.
including updates by floppy disk, CD ROM, radio
106

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1
Status Messaging
play individual buildings. These maps can
then be linked to building plans, street maps
The ability of the mobile resource to update
are also available to replace the map books
the central mobilising computer of any change
carried on vehicles.
of status instead of using a voice radio or cel-
lular telephone scheme. This facility should
Hydrant and water main information may
also incorporate the ability to send other stan-
also be superimposed on the maps so that the
dard messages, for example, assistance and
information resources of the Brigade are
stop messages, and should have a free text
available to all mobile terminals.
option to cater for any non standard messages.
Clearly, mapping data files are quite large.
2
Risk Information
Therefore, storing the maps centrally and
transmitting the data on demand would
Information gained from the inspection of
require high transmission rates, cause con-
premises, under the relevant section of the
gestion on the radio network and be expen-
Fire Service Act, shows the layout of the
sive. Currently, it would be better to store this
premises, the utility supply inlets and isolat-
type of information on the mobile data termi-
ing points, the location of water supplies and
nal hard drive (if available).
any risks to fire fighting. This data, which has
traditionally been held in paper form, lends
6
Automatic Vehicle Locating Systems
itself to being held electronically, thus mak-
(AVLS)
ing it available to all mobile data terminals
and centrally on the brigade's own network.
AVL systems have been available commer-
Building plans and maps may also to be
cially for some years. It has only been more
linked to this risk information.
recently that the Fire Service has investigated
the technology for its own use
(see DCOL
3
Brigade Information
8/1997, in Scotland DFM 8/1997).
Brigade orders, fire fighting information,
There are two basic systems in use; land
operational and technical procedures, any
based and satellite. The vehicle is fitted with
information produced by Brigades or from
a suitable AVLS receiver which, following
other sources may be held in an easily retriev-
the reception of signals, allows the geograph-
able format so that the Officer-in-Charge of
ic position to be computed and then transmit-
an operational incident has all the informa-
ted to a central mobilising system. The posi-
tion available.
tion of the vehicle is then displayed on a map
at the central control.
4
Hazardous Information
These systems have varying degrees of accu-
Information relating to hazardous substances
racy but care must be taken when attempting
may either be held on the mobile or centrally.
to predict the precise location and direction of
Chemdata, for example, when held centrally,
movement of a vehicle using this system. It is
can be distributed by radio and only compris-
possible for example, that the AVL system
es of a relatively small amount of data.
could indicate that a vehicle is located close
to the scene but it transpires that it is on the
5
Graphical Information Systems (GIS)
wrong side of a river or motorway to attend
the incident. (See AVLS, Chapter 7.)
GIS software, which requires mapping data,
gives the operational crews access to maps of
7
Vehicle Telemetry
the Brigade area, ranging from
1:5().()()()
raster based maps to vector based maps,
With the provision of a processor on a vehi-
which enable the operator to zoom in to dis-
cle and a wireless connection with a central
Communications and Mobilising
107

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point it is possible to send telemetry informa-
tion. For example, information on the vehicle
engine systems could be routed to the
Brigade's transport department or show quan-
tities of water, foam or other operational con-
sumables to the Control Centre or mobile
control unit.
12.7 Mobile Control Units
With the development of reliable data transmission
technology and vehicle based computer systems,
mobile control vehicles, used for major incident
command and control, are now being equipped
with IT systems linked to brigade computer net-
works and mobilising systems.
These vehicles include complex computer systems
and voice/data message handling facilities.
Bespoke software packages have been developed
specifically for this purpose.
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Communications
Chapter
and Mobilising
13
Chapter 13 - Breathing Apparatus
Telemetry
There is an increasing need to provide firefighters,
tus Entry Control Officer where the data can be
particularly those protected with breathing appara-
used to provide information which can be used to
tus, with enhanced information to improve both
facilitate better control of the incident and to
their safety and operational effectiveness. This
improve firefighter safety.
information could include, for example, informa-
tion on remaining cylinder contents and respiration
The provision of a radio data link between fire-
rates, ambient and body core temperature, heart-
fighters and those controlling the incident will also
rates, etc.
permit the remote signalling of other safety sig-
nals, including the transmission of information to
This data can be displayed to the wearer in full, or
the breathing apparatus Entry Control Officer of a
more practicably in an abbreviated form, perhaps
message in a data format indicating the automatic
by means of a display in the firefighter's breathing
or manual operation of a breathing apparatus
apparatus facemask. They can also be recorded in
Distress Signal Unit, and the transmission of a
an electronic data-base and downloaded at the con-
message in a data format causing the operation of
clusion of the incident, to provide a record which
an Evacuation Signal either to all in the risk area or
can be added to personnel records and used in the
selectively.
investigation of any injury or malfunction of the
apparatus.
It also facilitates the signalling of a radio message
in a data format indicating that the operator is
It is also possible to transmit some of this data by
withdrawing from the risk area for reasons of per-
radio to those controlling the incident, including
sonal safety. This last information, particularly if
the Incident Commander or the breathing appara-
more than one team signals this, will assist the
Figure 13.1 Radio
Distress Signalling Unit.
Radio Distress Signalling Unit
(Graphic: Marconi)
Functions as an Automatic Distress Signal Unit
Intrinsically safe
Transmits Distress Alarm message
Transmits Withdraw message
Receives Evacuation message
Receives Selective Evacuation message
Transmits Data from external source
109

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Figure 13.2 Entry
Control Unit.
(Graphic: Marconi)
Can communicate with up to 50 RDSUs
Receives Distress Alarm message
Receives Withdraw message
Transmits Evacuation message
Transmits Selective Evacuation message
Shows status of RDSUs
Stores event log
Receives Data from RDSU
Figure 13.3 Telemetry in use during trials.
{Photo; Essex Fire and Rescue Service)
Incident Commander in deciding whether emer-
based on the use of a dedicated radio frequency in
gency evacuation of the risk area is justified.
Home Office regulated radio frequency bands,
supported by a Type Approval (MG41) specifica-
The Home Office has developed a User
tion and a common-air interface.
Requirement (JCDD/40) for fire service telemetry
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Figure 13.4 Telemetry in use by Breathing Apparatus Entry Control Officer.
This User Requirement specifies the minimum
functionality for such equipment, which includes
remote signalling of Distress, remote signalling of
Evacuation, Selective Evacuation, and signalling
that the operator is withdrawing for reasons of per-
sonal safety. It allows the equipment to be com-
bined with, and provide the functionality of, an
Automatic Distress Signal Unit. It also allows
connection by means of a standard interface, and
transmission of data to and from operator-worn
equipment providing enhanced functionality such
as cylinder contents, temperature and so on. A sim-
ilar connexion is specified for the remote element
of the system to allow the use of equipment for
managing the incoming data.
Communications and Mobilising
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Communications
and Mobilising
Chapter 14 - Sub-surface
communications
Although there are exceptions, underground tun-
on one of the UHF two-frequency 'simplex' inci-
nels and similar structures are normally designed
dent channels on permanent talk-though, and used
for use for transportation, mineral excavation, car-
in conjunction with fire service standard handheld
parking and storage purposes. Apart from under-
radios. Any number of such base stations can be
ground car parks, the structures are often quite old
linked together by means of a simple audio cable
and, as a result, neither designed or built to ideal
to provide seamless communications. In effect any
standards.
handheld radio within range of one base station
can communicate with any other handheld radio
The characteristics of each tunnel or structure will
within range of any base station.
vary greatly, a tunnel may be nothing more than a
short horizontal tube cutting through a hill, or it
The distance between base stations is limited by
may be a vast underground complex with many
the physical length of the connecting cable (100m
tunnels, access points and service and customer
in the trials) and by the maximum radio range
facilities. Tunnels under construction will give rise
achievable in the specific risk using UHF handheld
to different problems.
radio radios.
The following applies to any building which is
Typical coverage using six base stations were:
constructed completely or partially below ground,
and includes any tunnel constructed as a railway, a
1150m in a Railtrack tunnel (compared with
roadway or for any other purpose that might attract
350m using a single base station). The limit
a fire brigade attendance. It could include, for
in this case was the length of connecting
example, service access to large shopping, indus-
cables.
trial, hospital, office and housing complexes.
810m in a BT cable tunnel (compared with
For practical purposes there is no penetration of
160m using a single base station).
the surface by any of the radio frequencies used by
the fire service for normal above-ground commu-
The Home Office has produced a specification,
nications. Technical Bulletin
1/1993 provides
MG49, for this type of equipment to enable
guidance on Operational Incidents in Tunnels and
brigades to carry out their own procurement.
underground structures and includes, as Part
3,
Guidance on Communications in these risks.
In operational use, one base station might be
established on the surface. A Breathing Apparatus
In September
1997 the Home Office completed
team would then enter the risk area carrying one
successful trials of a low-cost technique for
or more additional base stations and the associat-
improving fire service at-incident UHF radio
ed connecting cables, deploying a connecting
communications.
(Trial reports were issued in
cable as they advance. The first base station auto-
DCOL 1/1998 Item C, in Scotland as DFM
matically emits a repeated tone so that the BA
2/1998 Item C.)
team can discern when they reach the limit of
radio coverage from that base station. At this
The trial comprised a number of self-contained
point they can establish a second base station and
and handheld radio UHF base stations, operating
connect it to the first base station thus providing
CommunicationsandMobilising
113
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Multi-way Socket at rear of the Unit allows
Green light indicates
additional Units to be connected in series via an
Red light indicates repeater
Audio Cable
Stub Aerial
switched on
Stub Aerial
On/Off Switch
Multi-way Socket
On/Off Switch
Audio Cable connected
Carrying Handle
Carrying Handle
to repeater
Figure 14.1 Home Office Repeater Unit.
Figure 14.3 Home Office Repeater Unit.
(Photo: Devon Fire and Rescue Service)
(Photo: Devon Fire and Rescue Service)
Figure 14.2 Home Office Repeater Unit.
Figure 14.4 Sonic UHF/UHF Repeater Unit.
(Photo: Devon Fire and Rescue Service)
{Photo: Devon Fire ami Rescue Service)
continuous coverage from the surface to beyond
i.e., the second base station, once connected and
the second base station.
activated, will provide its own coverage area.
Using this method of deployment coverage will
The team can then proceed further into the risk
overlap that already achieved from the first base
area, deploying further cables and base stations as
station. There is also the possibility of quasi-syn-
necessary. Each base station would transmit a
chronous interference beats.
unique identity tone.
The foregoing arrangements can be improved by
A technical disadvantage of this method of deploy-
establishing 'ideal' locations for base stations as
ing the equipment is that it does not maximise the
part of incident pre-planning. Connecting cables
range achieved because it ignores the potential
could be pre-laid and base stations could even be
additional coverage which can be achieved when a
installed at appropriate risk sites.
second (or subsequent) base station is deployed,
114

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Communications
and Mobilising
Chapter 15 - Potential hazards of using
radio equipment
IN FLAMMABLE ATMOSPHERES
15.1 Explosion Protection •
Standards
NEAR EXPLOSIVES OR IN
HOSPITALS
In the European Union (ELI), standards for electri-
cal equipment designed for use in flammable gases
Special precautions are necessary when working in
and vapours are those approved by the European
areas where a potential ignition or explosion haz-
Committee for Electrotechnical Standardisation
ard exists. These could be due to the presence of
(CENELEC). Such equipment may be certified as
flammable dusts, gases or vapours, such as in oil
meeting the relevant standard by an EU approved
refineries, petrol storage depots, some factories
Certification Body. The relevant EU standards for
and commercial premises, coal mines, etc. The
Intrinsic Safety are drawn from EN50 014, EN50
introduction of electrical or electronic equipment,
020 and EN50 039.
such as a radio, by firefighters to such environ-
ments may constitute an ignition hazard.
Terminal equipment in current use in the fire ser-
vice may have been manufactured to comply with
Where such environments are known to exist, or
an earlier standard, e.g., British Standard
1259,
are suspected, then the electrical equipment needs
1958 or a BASEEFA standard SFA 3012 1972. This
to be safe for such use. This means that such
equipment can continue to be used until replaced.
equipment should be designed in such a way that it
does not present a hazard and that it should be cer-
Outside the EU other standards exist. In particular,
tified accordingly. There are a number of design
in the USA and those parts of the world where
concepts for achieving this of which the most com-
US standards prevail, equipment is certified to stan-
mon for radio terminals is that of 'Intrinsic
dards specified by either Underwriters' Labaratories
Safety'. Any equipment designed to be safe in
or Factory Mutual Research Corporation.
such environments is generically described as
'explosion protected'.
For the UK fire service the recommended standard
for general applications where a potential ignition
Additional precautions are also necessary when
hazard exists is for equipment that is certified for
using radio transmitters in the vicinity of explo-
use in Zone 1 with gas group IIC and a maximum
sives, ignition hazards or other devices that may be
temperature rating of T4. Such equipment would
adversely affected by radio transmissions. This
be indelibly marked EEx ib IIC T4 (or T5 or T6).
section deals in some detail with the technical
It is also recommended that such equipment
aspects of terminal equipment to be used in poten-
should satisfy a degree of ingress protection of at
tially flammable dusts, gases or vapours. It con-
least IP54 to EN60 529.
cludes by giving operational advice and guidance
on precautions to be taken by firefighters when
It is recommended that radio equipment purchased
using radio transmitters in potentially flammable
for use with breathing apparatus should, as a min-
or explosive atmospheres and use of radio in the
imum, conform to this standard. The equivalent
vicinity of explosives, petrol stations and medical
US standards are Underwriters' Laboratories
devices.
UL913 or Factory Mutual Class No 316.
Communications and Mobilising
115

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15.2 Ignition Sources
The presence of radio terminal equipment in a
potentially explosive, or flammable, dust, gas
or vapour can give rise to a number of possible
hazards from which ignition might result.
These include overheating of the radio terminal
during use or, more likely, during fault condi-
tions. In modern mobile radio terminals from
reputable manufacturers this is most unlikely
to occur under any working conditions when
the equipment is fully serviceable and operated
correctly.
The other potential dangers from the use of radio
terminal equipment arises from the possibility of
sparking. Sparks of sufficient energy to cause igni-
tion may be produced by two quite distinct mech-
When transmitting, they may also introduce a
anisms, as follows:
risk of inducing a current in a conductor, causing
remote sparking and ignition or some other
(1) Sparking may occur when contacts are made
unwanted consequence.
or broken in circuits carrying electric cur-
rents, or containing sources of electrical
energy; and
(2) Whenever a radio transmission is made the
electro-magnetic field radiates radio frequen-
cy voltages in all conducting materials in that
field. The induced voltages in adjacent
conducting elements, or between conducting
elements and 'earthy' conductors, may be
sufficient to break down intervening insulat-
ing layers of oxidation, grease, air, etc., and
cause dangerous sparking. This hazard is
directly related to the nature of the environ-
ment, the characteristics of the transmission
The risk from any 'fixed' mobile radio terminal
(power, type of modulation, etc..) and the dis-
equipment should be minimal since it is expected
tance of the antenna from the hazard.
that any potential hazard should have already
taken into consideration before siting is decided.
15.3 Protective Measures
However, some brigades employ transportable ter-
minal equipment which may be used, for example,
Fire service mobile radio terminals
(with an
as temporary controls or talk-through stations for
expected transmit power between
5 Watt and
special purposes. Such terminal equipment gener-
25 Watt) potentially introduce all of the hazards
ally has transmitter power of
5-25 Watts and,
described in paragraph 3 above into the risk envi-
therefore, the potential risk is comparable to that of
ronment. There is also a potential risk that the
a vehicle installation but it may be used in loca-
antenna of a vehicle mounted radio may directly
tions inaccessible to vehicles. This category of
touch a conductor during transmission causing
equipment should not be overlooked in any hazard
sparks.
assessment or the drafting of relevant orders.
116

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For relatively low-powered handheld radio termi-
that compartment can be locked and the key
nal equipment (typically less than lWatt) the max-
retained outside the hazard area. In ordinary fire
imum radiated power is usually insufficient to cre-
brigade use such a fitting may be an inconve-
ate induced currents in adjacent conductors.
nience.
Potential ignition hazards with handheld radio ter-
minals are, therefore, limited to the development
To obviate the possibility of components over-
of dangerously high temperatures, and sparking
heating, current limited devices
(often resistors)
caused by making or breaking electrical circuits.
have to be fitted which may reduce performance.
High temperatures are only likely to exist in fault
Extra thermal insulation may have to be provid-
conditions, e.g., by a component failure or break-
ed, making the equipment more bulky than it
down of insulation and steps can be taken to pre-
would otherwise have been. The mandatory dis-
vent internal sparking that has sufficient energy to
tance separations of components, and conductors
ignite a flammable or explosive dust, gas or
on printed circuit boards, may also affect equip-
vapour.
ment size.
Thus, it is a practical proposition to design an
Requirements for special materials or plating, nec-
handheld radio terminal which can be used with
essary to withstand long-term exposure to certain
safety in a potentially hazardous environment, i.e.,
chemicals, involve considerable additional cost; as
explosion protected equipment. Explosion protect-
does the incorporation of all the other non-stan-
ed terminal equipment nearly always exists as well
dard requirements mentioned. These are some of
in a normal, un-protected form. In comparison
the factors which combine to make the idea of
with the non-protected terminal equipment the
using this equipment for all purposes quite unat-
protected equipment will often have a reduced
tractive both from size and costs.
maximum transmitter power, be more expensive to
procure and maintain, will require 'special' batter-
15.5 Selection of Explosion
ies and may have reduced functionality.
Protected Equipment
The selection of protected types of handheld radio
The current recommendation to the fire service is
is also likely to be much less than un-protected
that radio equipment purchased for use with
types and purchasers may have a limited choice of
breathing apparatus should be certified by an EU
equipment from which to select equipment for pro-
approved Certification Body for use in Zone
1
curement.
with gas group IIC and a minimum temperature
rating of T4. Such equipment will be indelibly
15.4 Intrinsically Safe Design
marked as follows:
Criteria
EEx ib IIC T4 (or T5 or T6)
The requirement for explosion protected equip-
ment certified for use in flammable, or explosive
Certified equipment must cater for worst-case con-
dusts, gases or vapours, means that the equipment
ditions for the whole of its working life under con-
must be incapable of causing ignition, even under
tinuous operation in a hazardous environment. It
fault conditions or when subjected to gross mis-
must also take into account carelessness, clumsi-
handling. This necessitates design features which
ness and ignorance on the part of the operator.
often have performance penalties in normal condi-
tions.
In perspective, the few occasions when faults will
develop in modern personal radio sets are consid-
It is usually necessary, for example, to make it
ered and the fact that fire service personnel are
impossible for batteries to be fitted or removed
trained to comply with instructions regarding care
within the hazard area, because of the potential
of this equipment, the occasions when all the
danger of sparking during this process. Therefore,
above special design features would be needed is
it is usual for the battery compartment of such
small.
equipment to be fitted with a key-operated lock so
Communications and Mobilising
117

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15.6 Radio Use in the Vicinity of
15.8 Radio Use in the Vicinity of
Explosives, etc.
Air Bags
Radio transmissions impose a potential ignition or
Because of the potential, but remote, danger of
initiation hazard near commercial explosives, mil-
actuating an air bag in a vehicle which has been
itary ordnance
(including nuclear weapons)
and
involved in a road traffic accident in which an air
terrorist devices.
bag has not actuated, no radio terminal should be
used to transmit a message within
10m of the
vehicle.
Current guidance to the fire
Additionally, to avoid the remote possibility of
unwanted actuation, no handheld radio terminal or
and police services is that no
handheld cellular radio terminal should be used
radio transmitting equipment
inside a vehicle equipped with an airbag unless it
is connected to an aerial system external to the
should be used within 10m of
vehicle.
the risk, that only handheld
terminal equipment (less than
15.9
Radio Use in the Vicinity of
5 Watt) should be used within
Medical Devices
10m and 50 metres, and that
There is a potential hazard that radio transmissions
vehicles fitted with mobile
may have unwanted effects of medical devices.
radio terminals should not
No fire service handheld radio can be considered
be taken within 50m of the
as being safe to use in radio sensitive areas of hos-
risk unless the radio is
pitals, nor can any 'safe-distance' be recommend-
ed. Accordingly, handheld radios should only be
switched off.
used for transmission in hospital buildings in
exceptional circumstances and where the circum-
stances are unavoidable. If a handportable radio
has been used then this should be reported locally
In this context, many modern radio terminals,for
to the hospital/medical staff so that they can initi-
example, data capable radios, 'trunked' radios and
ate whatever checks they might think necessary to
radios using public cellular or public data services
detect and rectify any effect that the transmission
are capable of auto-transmission. Unless the trans-
might have had.
mission function can be inhibited by the user such
equipment should be switched off if it is necessary
In this context, many modern radio terminals, for
to take it into the protected area appropriate for the
example, data capable radios, 'trunked' radios and
type, e.g., if it is necessary to take a public cellular
radios using public cellular or public data services
radio terminal to within 10m of the hazard.
are capable of auto-transmission. Unless the trans-
mission function can be inhibited by the user, such
15.7 Radio Use in Vicinity of Retail
equipment should be switched off if it is necessary
Petrol Stations, etc.
to take it into a hospital premises.
Current guidance to the fire and police services is
Where a hospital has placed a restriction on
that similar restrictions to those applicable to the
the public use of cellular radios then these
use of radio terminals in the vicinity of explo-
restrictions should also be taken as applying to
sives should be applied in respect of retail petrol
handportable radio terminals or any public
stations, petroleum transfer stations and oil
cellular radio terminals that may be used by
depots.
firefighters.
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15.10 Radio Use within Silos
The presence of a radio may cause ignition of any
flammable dust, gas or vapour that exists in a silo.
There is also a remote possibility that a transmis-
sion from a handheld explosion protected (intrinsi-
cally safe) may result in a spark caused by an
induced current.
Accordingly, similar restrictions
to those applicable to the use of
radio terminals in the vicinity
of explosives should apply to
the use of radios near or within
silos until it has been established
by monitoring that there is no
trace of a potentially flammable
dust, gas or vapour within
the silo.
Notwithstanding the foregoing, the Officer-in-
Charge may decide to permit the limited use of
explosion protected
(intrinsically safe) hand-
held radios or telemetry equipment within a
silo, provided that a risk assessment has been
carried out and it is considered that the opera-
tional and safety benefits of so doing exceed the
remote risk of ignition.
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Communications
and Mobilising
Glossary of terms and abbreviations
Address Point
Ordnance Survey digitally co-ordinated postal address data.
Alerter system
A call-out system utilising pocket-alerters, carried by retained firefighters,
which are triggered by a radio signal transmitted by a remotely controlled
alerter transmitter usually located at a fire station.
Algorithm
A procedural model used when computing complicated calculations
(e.g., routes and drive times).
Analogue
An analogue signal is one which can vary continuously, taking any value
between certain limits. The human voice, for which the public telephone
network was designed, is an analogue signal varying in frequency and
volume.
ACD
Automatic Call Distribution.
AFA
Automatic Fire Alarm.
AVLS
Automatic Vehicle Location Systems.
BA Interface
An interface designed to permit a handheld radio set to be used in con-
junction with breathing apparatus.
Bandwidth
The range of signal frequencies which can be carried by a communications
channel subject to specified conditions of signal loss or distortion.
Base Station
The transmitter/receiver and associated equipment at a fixed location.
CACFOA
Chief and Assistant Chief Fire Officer's Association.
Call sign
An identifier, normally comprising a name, numbers or letters, by which
an appliance or officer is identified when being called by radio.
CCTV
Closed Circuit Television.
Cellular
A technique used in mobile radio telephony to use the same radio spec-
trum many times in one network. Low power radio transmitters are used
to cover a limited area or 'cell' so that frequencies in use can be re-used in
other parts of the network.
Communications and Mobilising
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CHEMET
Chemical Meteorology.
CIMAH
Chemical Incident Major Accident Hazard.
CLI
Calling Line Identity.
Concentrator
Any communications device that allows a shared transmission medium to
accommodate more data sources than there are channels currently avail-
able within the transmission medium.
COSHH
Control of Substances Hazardous to Health.
CTCSS
Continuous Tone Controlled Signalling System. In PMR, a method of
using sub-audio tones to effect selective transmissions to a mobile or
group of mobiles.
Cycle
The portion of the radio wave between successive crests or troughs, which
is repeated over and over again to form the continuous wave.
DCOL
Dear Chief Officer's Letter.
DDI
Direct Dial In.
DIEL
OFTEL's advisory committee on telecommunications for Disabled and
Elderly People.
Digital
Communications procedures, techniques and equipment where information
is encoded as either a binary ' 1' or '0'.
Digital data network
A network specifically designed for the transmission of data, wherever
possible, in digital form.
DTI
Department of Trade and Industry.
Duplex working
A communications technique in which it is possible to transmit and
receive simultaneously e.g., as in an ordinary telephone conversation.
EAs
Emergency Authorities.
EACC
Emergency Authority Control Centre.
ERP
Effective Radiated Power.
ESM
Emergency Services Manager.
ETD
Extension Trunk Dialling Network.
ETSI
European Telecommunication Standards Institute.
Fire alarm call point
A device to operate the fire alarm system manually.
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Fire alarm system
A fire alarm system comprising components for automatically detecting
fire initiating an alarm of fire and taking other action as arranged. The sys-
tem may also include manual call points.
Frequency
The number of cycles of wavelengths, which appear to pass a given point
in a specified time, usually one second.
FFSK
Frequency Fast Shift Keying.
FMG
Frequency Management Group.
FRNT
Front Office Directory.
Geocode
Assignment of a specific grid reference to an incident, address or
rendezvous point, etc.
GIS
Graphical Information Systems.
GPO
General Post Office.
GPS
Global Positioning System - Navigation system developed by the United
States Defence Department as a world-wide navigation and position
resource for both military and civilian use. It is based on a constellation
of twenty four satellites orbiting the earth at a height of over 20,000
kilometres. These satellites provide accurate three dimensional position
and velocity as well as precise time, and act as reference points from
which receivers on the ground triangulate their position.
GSM
Global Systems for Mobile communications - European standard for digi-
tal cellular networks operating at 900 MHz world-wide and supporting
data transmission.
GTPS
Government Telephone Preference Scheme.
Handshake
A predefined exchange of signals or control characters between two
devices that sets up the conditions for data transfer or transmission.
Hertz (Hz)
Measurement of frequency where one Hertz equals one cycle per second.
Hilltop Sites
Or Main Stationsare normally on high, open ground (hence the alterna-
tive name) from which it is possible to 'see', in the radio context, a con-
siderable portion of the brigade area. 'Main' equipment operates in an
'omni-directional' mode to cover the largest possible geographical area.
HOFMG
Home Office Frequency Management Group.
ICCS
Integrated Communications Control System.
ICU
Incident Control Unit.
Inmarsat
International Maritime Satellite Organisation.
Communications and Mobilising
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Interface
A shared boundary, a physical point of demarcation, between two devices
where the electrical signals, connectors, timing and 'handshaking' are
defined. The procedures, codes and protocols that enable two entities to
interact for the meaningful exchange of information.
IS
Intrinsically Safe Equipment designed to be operated safely in an environ-
ment consisting of flammable or explosive dusts, gases or vapours.
ISDN
Integrated Services Digital Network - An internationally agreed public
network offering switched end-to-end digital services for voice and data.
KiloStream
The registered trademark for BT's digital network services, used for
connecting a variety of high-speed applications including computers,
LAN interconnect and switchboards.
LAN
Local Area Network is one which spans a limited geographical area,
usually within one building or site, and interconnects a variety of
computers and terminals, usually at very high data rates.
Leakv feeder
A linear aerial which radiates radio signals throughout its length. Such
an aerial is particularly suited to facilitating radio communications in
sub-surface premises in conjunction with a UHF base station.
Link Transmitters
And Link Receiversprovide communication between the control station
and the main stations. 'Link'equipment operates in a 'Point-To-Point'
mode in which every effort is made to send signals only in the intended
direction and only so far as necessary.
Main scheme radio
A radio system giving wide area radio coverage throughout the area
covered by the mobilising control.
Main Control
'Control Station' or simply 'Control'. This is the place where the
operators who control the scheme, and the main transmitting and
receiving equipment of a scheme are located.
Main Transmitters
And Main Receiverssend radio signals to, and receive radio signals from
'mobiles'.
'Mobiles'
Are the transmitter/ receivers fitted in fire appliances and other
vehicles.
MIS
Management Information Systems.
MMC
Monopolies and Mergers Commission.
Modem
Modulator/Demodulator - device for converting analogue signals into
digital signals and vice-versa.
Multi-station scheme
A scheme served by several main stations e.g., a large country scheme.
NOU
Network Operations Unit.
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OAC
Operator Assistance Centre.
OFTEL
Office of Fair Trading for Telecommunications.
Out-stations
All radio stations in a scheme, including two-way fixed and mobile sets
and fixed receivers but excluding main stations, main and sub-controls.
PABX
Private Automatic Branch Exchange.
PCNs
Personal Communications Networks.
PCS
Personal Communications Systems.
PDA
Pre-Determined Attendance.
PECS
Public Emergency Call Service.
PMR
Private Mobile Radio - A network developed for one particular organisa-
tion, usually an emergency service.
POCSAG
Post Office Code Standard Advisory Group
Private wire circuit
A dedicated telephone circuit permanently connected between two or more
points for transmission and reception of speech and/or data.
Protocol
A set of rules governing information flow in a communication system.
PSTN
Public Switched Telephone Network.
PTO
Public Telecommunications Operator.
Public Address
A loudspeaker system which may be operated by remote control from a cen-
tral control room or locally for both operational and administrative purposes.
PWIT
Public Warning and Information by Telephone.
RBRT
Racal BR Telecoms Ltd.
RIC
Receiver Idendity Code.
RIDDOR
Reporting of Injuries, Diseases and Dangerous Occurrences.
RFCPU
Radio Frequency and Communications Planning Unit.
Roamer
Is the term used to describe a person who takes their mobile phone abroad
with the specific purpose of making or receiving calls.
Roaming
Is is the term used to describe the ability for a person to take their mobile
phone abroad and be able to make and receive calls in a country with
which their own network operator has signed a roaming agreement.
Communications and Mobilising
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Running call facility
A facility at a fire station which enables a running caller to give an alarm
of fire.
Secondary Control
A mobilising control (possibly in another fire brigade area) to which, in
an emergency, the functions of receiving emergency calls and mobilising
appliances are passed, in the event of an evacuation of the normal
mobilising control.
Simplex working
A communication technique in which it is not possible to transmit and
receive simultaneously.
Single frequency scheme
A scheme using one common frequency for transmitting and receiving by
all stations.
SMS
Short Message Service.
Switch
A switch is the core element of a radio or telephone system. It provides
control, management and the routing of voice and/or data calls between
radio system infrastructure, mobiles and portables, telephones, controllers
and computer terminals.
Talk-through
A facility on two-frequency radio schemes which interconnects incoming
and outgoing channels. Used to enable out-stations on a scheme to hear
and talk to each other.
Telemetry
A means of establishing measurement remotely.
Terminal
A device for sending and/or receiving data on a communication channel.
TODS
Telephone Operator's Directory System.
TOPS
Total Operations Processing System.
Transportable Radio
A portable transmitter/receiver of roughly the same power as a mobile set.
TUES
Text User's Emergency Service.
Two-frequency operation
A means of operation whereby radios receive on one frequency and trans-
mit on a different frequency (also known as double-frequency peration).
UHF base station
A radio installation which allows boosted signals of double frequency
operation with UHF equipment. This equipment is usually provided as a
mobile version but. exceptionally, e.g., at major airports, there are autho-
rised fixed installations.
WAN
Wide Area Network - Interconnects geographically remote sites.
WARC
World Administration Radio Conference.
Wavelength
The distance between successive crests, or successive troughs.
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