The Initial Speech and Telegraph Emergency Networks
This topic describes both the United Kingdom Warning and Monitoring Organisation (UKWMO) and Regional Government Headquarters (RGHQ) communications from its inception in the early sixties, through the seventies and early eighties. Both network were linked together, so they are treated as a single network. A Home Office review identified the need for an upgrade which took place during the mid-eighties and replaced the systems described here by those on the 'Era 2' page tab.
Speech and Telegraph Networks in ERA 1
Overview of the Networks in the U.K.
This topic looks at the networks used by the UKWMO in their reporting of nuclear detonations and fallout warning role and the Government Control Network (GCN) operated for the local and regional government organisation. Although the UKWMO and RGHQ networks were separate entities they were joined between the UKWMO Group and the RGHQ serving the county where it was located.
Reproduced from Ordnance Survey map data by permission of the Ordnance Survey © Crown Copyright 2001.
Both the UKWMO and GCN were of a similar design and interconnected so will be treated as one. Both networks used Post Office Telephones landlines to link between nodes. A single circuit would carry both speech and telegraph signals, at each node the speech circuit terminates on a telephone switchboard and the telegraph circuit in the message centre. Many of these links had a duplicate standby radio circuit provided by the Home Office making it totally independent of the GPO network.
The UKWMO Private Network
Within the UKWMO there were two distinct networks. One linked Royal Observer Corp (ROC) Posts to their Group Headquarters for speech only, this is dealt with under the Menu Tab: Communications / ROC Post Era 1. The other linked adjacent UKWMO Group Headquarters together. This network had two sub-networks one for speech and the other telegraph. Telegraph is for sending hard copy messages between one or more places. At this stage of development, there was only a single landline with a standby VHF radio link between the adjacent groups carrying both speech and telegraph signals.
The UKWMO network only connected the adjacent Royal Observer Corp Group Headquarter. By the use of message centres it was possible to send messages between any two locations even though they were not directly connected. The message centre could also broadcast the same message to many locations if this was desired.
Of the five UKWMO Sector Headquarters, only Preston and Lincoln Sectors were directly connected as they are adjacent, therefore all other inter-sector traffic had to be relayed via another UKWMO Group. During the late 1970ís the five Sector Headquarters traffic had grown to an extent that warranted direct links. Unlike the inter-group landlines, these newly provided circuits didn't have a radio standby.
Regional Government Headquarters Network
The Government Communications Network (GCN) like the UKWMO network had two sub-networks, one for speech and the other for telegraph. This network was centred around the RGHQ, linking it with adjacent RGHQs, and the County Council Wartime Headquarters within its zone, Armed Forces headquarters (AFHQ). It had a landline with a standby UHF radio link to the UKWMO Group HQ(s) monitoring the towns and cities within its zone.
I don't have a diagram to show the GCN network during the ERA1 time period. Instead here is an extract from a declassified document, the UKCICC(H) Joint Signal Instruction. At this time the document was written the Sub-Regional Headquarters (SRHQ) was the name for the RGHQ.
UKCICC Joint Signal Instruction Part 5
The Government Control Network
119. This network provides the following facilities:
a. A landline and radio link between adjacent SRHQs, both within and
outside individual regions.
b. A landline and radio link from the SRHQ to each county wartime
headquarters (both main and standby) within the sub region. In the case
of Greater London, the SRHQ will be linked by line and radio to the
headquarters of the 5 London groups and, in addition, each group will have
a "speech only" radio link to an alternative SRHQ.
c. A tape relay centre at each SRHQ, providing duplex (two-way) teleprinter
facilities to adjacent SRHQs and to county wartime headquarters (both main
d. A landline link from each SRHQ to the Emergency Manual Switching Scheme
e. A landline and radio link from each SRHQ to a selected Group Headquarters
of the United Kingdom Warning and Monitoring Organisation (UKWMO).
f. A "speech only" radio link from each SRHQ to the headquarters of the
various police forces within the sub region.
g. A landline link between the main wartime headquarters of each county
and an appropriate police headquarters.
h. In the case of metropolitan counties, a landline and radio link
between the main or standby headquarters of the county and the
wartime headquarters of each metropolitan district.
j. In the case of Greater London, a landline and radio link between the
headquarters of each London group and the wartime headquarters of each
London borough within the group.
k. A "speech only" radio link between the headquarters of each London
group and neighbouring London group.
l. A landline link from each county wartime headquarters (both main and
standby) and each London group to the EMSS.
120. Where both landline and radio links are provided, they are complementary,
and terminate on common switchboards. The landline circuits carry simultaneous
teleprinter working, with the radio link providing an alternative circuit if the
landline circuit fails.
121. UHF radios are also provided between SRHQs and the aircraft and helicopters
of the regional air squadron to facilitate the passing of reconnaissance reports.
If the squadron are reinforced by other light civil aircraft, other telecommuni-
cations might have to be improvised.
122. As a further standby measure, in each sub region there will be a reserve
of up to 10 HF radio sets. These are transportable, have easily erected aerials
and are omnidirectional. They have facilities to recharge their batteries or to
operate off standby generators. Their range is about 20-30 miles and consequently
they could be used in the last resort to plug the gaps in the GCN. They will be held
under Home Office control within sub regions.
Note. This document refers to a number of topics covered elsewhere on this website. These topics are indexed on the top tabs or linked at the bottom of this page.
Para 120, The system for simultaneous speech and teleprinter working, is S+DX, found under the 'Related Topics' tab. There is a brief overview further down this page in the 'Telegraph and Speech over the same Landline' topic
Para 121, refers to a topic within 'To Military' found in this 'Communication' tab group.
Para 122, is believed to be LDN found under the 'Post Strike' tab.
Para 119, sub-paras D & L, the EMSS, found under the 'Related Topics' tab.
ERA 1 Telephony
From the 1960ís until the communications upgrade in the 1980ís the UKWMO Group, RGHQ and County Council bunkers had manual switchboards with a mixture of public telephone lines and private circuits for use by the extension telephones in the building.
Cord Manual Switchboard
Private Manual Branch Exchange
The small Private Manual Branch Exchange shown here has the capacity of 10 exchange lines and 50 extensions, is of the type used at small control centres, such as those operated by County Councils. The PMBX10+50 was a standard item used on the public network. An extension would have to ask the switchboard operator to ring another extension. For outside calls the operator connected the extension to an exchange line and may have dialled the external number too.
The larger multiple position switchboard may have been used on its own as a manually operated switchboard or in conjunction with an automatic switch. The automatic switches of this era were of the electromechanical type. The operator would connect incoming calls. Extensions could usually dial an external number by prefixing it with a nine but some establishments required the switchboard operator to connect the call. Calls to other bunkers over private circuits were usually connected by the operator.
The UKWMO and the RGHQ had their own private networks of landlines and radio links. An extension wishing to call another elsewhere in the private network would ask the switchboard operator to connect them. The operator would place the cord into the jack on the switchboard face and operate the 'ring' key. This would call the attention of the distant operator who would ring the distant extension. This could be quite a protracted process as each operator may be dealing other calls. There may be only one or two lines between switchboards so extensions may have to queue to get connected.
Post Office Emergency Network
During the nineteen sixties and the early seventies, long distance calls over 25 miles, were connected by the public telephone operator. In wartime that service would be compromised so the Post Office set up a small network of special switchboards in protected areas of telephone exchanges to maintain a long distance connection for emergency services. This network was known as the Emergency Manual Switchboard Service (EMSS).
Although automatic dialling of long distance calls became universal by the end of the seventies the EMSS network was retained throughout the Cold War period as it was assumed the public network would suffer badly in an attack. Before the digitalisation of the UK network in the late eighties the automatic long distance dialling network provided no alternative routing of calls should part of the network fail. Therefore it was important to retain a manual network which could adapt to a wartime situation.
The EMSS is described in its own topic if you wish to read more. Top of page, Menu Tab: Post Strike / EMSS
ERA 1 Torn Tape Telegraph Message Centre
This describes the functioning of a torn tape message switching centre like those used in the UKWMO Group Headquarters and Regional Government Headquarters (RGHQ) prior to their communications upgrade in the mid 1980's.
Their use was widespread beyond the UKWMO, as a child I recall a conducted tour at the USAF base at Croughton, Oxon. (Possibly 1967) Being shown the tape centre and the new 80-hole punch card system that had just been installed. They gave us a punched card that I kept for many years saying something like 'Welcome to RAF Croughton from the officers and servicemen of Autodin.' Some large companies had their own tape message centre too.
Each UKWMO Group headquarters and each RGHQ had its own message centre. They were connected to a small number of adjacent centres in their own network with a link at each node between the UKWMO Group and its RGHQ. The links normally worked over the landline but could be switched to an alternative radio link and would send messages in either direction. Each link had a paper tape reader connected to the 'send' and a paper tape perforator connected to the 'receive'. A teleprinter connected to a tape reader would convert paper tape messages to printed copies. A Teleprinter with a paper tape perforator or a punch unit created outgoing message tapes.
The telegraph network used a 5-bit baudot code sent at 50 baud, which is very slow by todayís standards but suited the mechanical devices it was designed for. The five hole code for each character was punched in a row across the width of a paper tape.
This type of paper tape was used by business telex and small scale use. For message centres it was desirable to have the message printed down the side of the tape to assist the operators in handling the messages. The small piece of paper punched out of the hole known as a chad is undesirable in a message centre. They create disposal problems and tend ingress into mechanisms causing faults. To overcome the problems a chadless tape was used which had a square hole cut on three sides and attached on the other.
Sending a Message
Torn Tape Centre
A typist would prepare a message by typing on a punch producing a paper tape or a teleprinter with a tape perforator. The message would start with a header indicating the destination(s) of the message, the message itself and a run out of blank tape. This was torn from the perforator and carried to the tape reader on the link to the desired recipient.
The tape was placed in the reader and the start button pressed. The teleprinter signals would be sent to the distant end, if that were a teleprinter the message would be printed on the paper roll. If it were another message centre, the signals would cause the associated tape perforator to reproduce the sent message tape. If the message were a broadcast it would be transferred to the next reader and sent again to that destination.
Receiving a message
An incoming message would be perforated onto paper tape and a lamp illuminated to indicate the arrival of the message. The operator would tear the tape from the punch and visually inspect the header. The tape would be transferred to a reader associated with a local teleprinter. This would print the message on a paper roll. The paper was torn from the machine and placed in the out-tray to be taken to the recipient.
Indirect and through messages
If the originating message was destined for recipient at a location without a direct link, or the direct link was faulty or destroyed by enemy action the tape would be sent to another message centre. On receipt the operator would inspect the header and see that it was not for their centre. If the message were for a destination which centre had a working direct link the tape would be placed on the reader of that link and sent. Otherwise it would be sent to another centre with a possible link. The choice of alternative centres is known as the 'routing'.
Flexibility and Economy
A torn tape message centre was a very efficient way to achieve full message routing throughout a network of locations without having to connect every one to the others. It is very flexible too as the operators can use their intelligence to work around a fault or non functioning centre.
When the UKWMO telegraph network was introduced in 1968 it was piggy backed on the existing speech network using Speech plus Duplex technology ( S+DX ). The actual network connecting the 25 Group Headquarters in the UK had 53 links. This economy of scale was possible as only adjacent headquarters were connected together. It still enabled a message to be sent from any point to another via one or more tandem relay points. Whereas a fully interconnected system would have required 300 links costing six times more, even though many links between remote points may never have carried a message.
The Teleprinter for the ERA 1 Telegraph Network
A teleprinter of the cold war era was a large Electro-mechanical device resembling an electric typewriter. There was a large public network of machines in the UK, which due to the high cost was almost exclusively for business use. The UK public network was dial up in a similar way to the telephone network but the two networks were not connected. Some large companies had the own independent network which more than likely used Post Office leased private circuits. The Post Office Telegrams division had its own 'TASS' private network up until the 1970's, used for sending public telegrams. This used Creed 47 designated as British Post Office No.11 machines that printed on a thin strip of gummed paper for sticking onto the telegram document.
Before the FAX machine became popular with businesses during the late 1980's, Teleprinters were favoured as an 'instant' communications medium as they produced a hard copy. The data rate, which was considered fast at the time, was 50 baud, with a 5-bit code plus 2.5 start and stop bits. The signalling was by sending 80 Volts Positive and 80 Volts Negative along the two wires. A good typist could type faster than the machine could send the characters, to prevent this happening the keyboard was mechanically locked to prevent a second key being pressed until the previous character had been sent.
Teleprinter No 7
Creed 7B for the TELEX Network
The original Creed 7B here on the right is shown in a configuration for the British Post Office TELEX network. The 7B could be used on point to point links and terminal points on the network but as it had no paper tape facilities. Separate tape perforators and tape readers were required. The large box under the desk but normally located in a more convenient place is the power unit providing the 80 volts DC signalling.
The No.7 designed in 1931 is ingenious consisting of hundreds of moving parts. This was the mechanical equivalent of the UART found in computer modems and decoded the 5-bit code and printed the character on the paper. Only capital letters, numbers and a limited number of special symbols were available.
Creed 7ERP with cover removed
An improved version of the No.7 the 7E used a different clutch arrangement overcame the problem where the 7B printed one character behind the one being received. In the photograph below this version of the 7E is the 7ERP as it includes a tape re-perforator (RP). The electric drive motor and speed governor (the black a white round box) which powered both the printing mechanism and keyboard can be seen at the front left.
Teleprinter No 15
PO Teleprinter No15
The Creed 444 introduced in 1966 and designated the British Post Office No.15 replaced the old noisy No.7 printers for business use. The new machines had two colour printing, a built in paper tape perforator and reader. They were much easier to use as they had an improved keyboard and could store keystrokes. Later on screen based telex machines were introduced, but the No.15 gave good service until the closure of the telex network.
Although the Teleprinter No15 became well established in the public network during the seventies I have little evidence it was adopted for the UKWMO networks by 1980. The reliance on a good mains supply may have made it unsuitable for use with standby generators.
Cabinets containing three printing perforator like the one here were installed in UKWMO group and RGHQ tape relay centres. The bottom unit is open with the printing perforator pulled forward into the maintenance position. A printed version of the punched hole message is printed along the outside of the tape. The punched tape exited through the front of the soundproof door ready to be torn off by the centre operators. Longer messages collected in a floor level tray.
At the top of the cabinet are three sets of supervisory lamps and control switches, one set for each tape perforator. As there is no message store in this system it was essential for the operator to ensure there was sufficient paper tape. An alarm was raised when the paper was low. The circuit had to be blocked to the distant end when the paper or print ribbon was changed.
Each link from a remote location required an individual printing perforator, necessitating a number of these cabinets. Somewhere like Coventry UKWMO Group HQ would have required three or four cabinets, for the links from seven adjacent Groups and two RGHQ's.
Telegraph and Speech over the same Landline / Radio Circuit
Economy Measures - Speech and Telegraph
At this time, the rental of landlines was very expensive, so to avoid having separate landline for Speech and Telegraph a very clever system known as Speech plus Duplex Teleprinter, S+D or S+DX was used in the UK Civil Defence network to carry duplex teleprinter signals over the same wires as duplex verbal communication. This system was not exclusive to Civil Defence, but was used in the public network too.
This drawing shows the principle of the arrangement. At each end of the Private Circuit (Landline) a box of electronics combines the inter-switchboard speech line with a bothway link to a teleprinter or torn tape message centre. A more detailed explanation is given in the topic S+DX listed in the Further Reading section at the foot of this page, or via Menu Tab: Related Topics / S+DX at the top of this page.
In both networks, the S+DX could be switched to the radio circuit should the common landline fail. A special jack panel was provided to switch from landline to radio. During weekend ROC exercises, a test of switching to radio standby circuits was usually undertaken for about an hour.
ERA 1 Radio Backup to Landlines
Within both the UKWMO and RGHQ networks radio systems were provided to act as a standby for the landline network.
The UKWMO network utilised single channel radio links in the VHF band. The more extensive RGHQ network radio links operated on UHF with both single channel per carrier and multiplexed links. The UKWMO radio links used Home Office Hilltop wireless stations equipped with standby generators already used for Police and Fire Brigade radio schemes. All three groups of users were Home Office departments so it made sense using the same hilltop sites. The radio equipment was supplied and maintained by the Home Office Department of Telecommunications (DTELS)
UKWMO Radio Links
Inter UKWMO Group Radio
VHF radio links were provided to supplement the landlines. These provided a duplicate speech circuit between switchboards and additionally the telegraph S+DX could be switched over to use this reserve path. The range of a VHF radio link is limited to 30-40 miles, so a number of tandem links were required to connect the long distances between Groups. At the Group HQ bunker, a windup mast carried a number of VHF 3 or 6 element yagi aerials, pointing at the nearby DTELS hilltop sites. The chain of hilltop sites had 6 element Yagi aerials carrying the links, one aerial was used for both transmitter and receiver. Some Hilltop sites would have more than one link between Group Headquarters passing through them.
VHF 6 Element Yagi
Here is a mast with a number of Six element yagi aerials exactly like those used on UKWMO links. The aerials are either mounted with their elements horizontal or vertical. Aerials at each end of the link will have the same element polarisation. An aerial of the opposite polarisation only receives a weak signal. This can be exploited to allow the same radio frequency to be used in the order of fifty miles away if the polarisation is different.
In this first era 1960-s - 1970's the bands were 147.000 - 147.300 MHz paired with 155.000 - 155.300 MHz which were a sub band of the larger 146 - 148 MHz and 154 - 156 MHz frequency assignment for Emergency Service use. An exclusive Civil Defence band 168.325 - 168.800 MHz paired with 174.025 - 174.500MHz was used for the UKWMO in accordance with notes N27 N29 in UK Table of Radio Frequency Allocations 1985, ISBN 0-11-513819-6
UKWMO VHF Link Details and Frequencies
The enlarged map shows all the individual radio links emanating from Wrexham, Shrewsbury, Coventry, Bedford, Lincoln and Norwich. And a partial set of information for the others. Where the routing of a radio circuit isn't known it is shown as a squiggly gray line. Appealing to ex-DTels staff - If you know the routing for any missing home defence radio links just a small part would be most helpful in building a bigger picture.
It has been suggested that not all the inter group radio links actually worked and some worked but had not been formally commissioned. All the VHF links were switched off as part of the W.A.R.C. project which changed the emergency service radio frequencies during the mid to late 1980's. The old UKWMO link frequencies were allocated to the emergency services when they migrated from 100 MHz, it was the intension to use the RN1 and RN2 networks described on the next page for the links.
RGHQ Radio Links
In this first era the bands used were 452.000 - 452.225 MHz paired with 466.000 - 466.225 MHz and some additional channels in the larger 451 - 453 MHz and 465 - 467 MHz Emergency Services band which was mainly used for Police personal radios. There were two other bands 455.875 - 456.000 MHz and 468.875 - 470.000 MHz exclusively used for RGHQ links.
Click to Show - The Detailed UHF Channel Plan
UHF Frequencies allocated for RGHQ UHF Network
LOWER CHANNEL PAIRS UPPER CHANNELS OTHER CHANNELS HEARD
452.000 466.000 455.8875 469.8875 450.850 464.850
452.025 466.025 455.9125 469.9125 451.150 465.150
452.050 466.050 455.9375 469.9375
452.075 466.075 455.9625 469.9625
452.100 466.100 455.9875 469.9875
Some of the Links to RGHQ 4.2
UHF 12 Element Yagi
The shorter wavelength of these UHF bands lends itself to the use of high gain aerial with many elements. This photograph of a local council control centre shows a 12 element UHF yagi aerial, typical of the type used on RGHQ links to councils and other users.
Compared with a UKWMO Group HQ, there were a large number of circuits radiating out from a typical RGHQ, which dictated a different linking arrangement. If they operated a single channel per carrier like the UKWMO there would be problems due to the large number of individual transmitters, receivers and aerials required at the RGHQ as well as the hilltop sites. A technique known as multiplexing allows a single radio channel to carry seven circuits. One circuit is carried at normal speech frequencies and six are translated to higher frequencies, the resulting combined output is used to modulate the radio transmitter. The radio receiver output is fed into a demultiplexer to separate the individual speech circuits. A pair of multiplexer / demultiplexer equipment is needed at each end of the radio system.
In this link map, the circuits from individual sites to the Thurfield mast are single channel links but the last hop to the RGHQ is a multiplexed link. A more detailed description of analogue speech multiplex process may be found on the further reading link at the foot of this page.