R.O.C. Observer Post Communications - ERA 1

This topic investigates the early communications systems used by ROC Posts. The TeleTalk and Warning receiver were installed in the early 1960's and in the 1970's master posts were equipped with a radio too.

Landline link to Group

Telephone, Observer AD163

Magneto Telephone with Headset

In the early 1960's the original magneto type telephone with a headset and breastplate microphone worn by the observer, "Telephone, Observer AD 163C" used since WW2, was replaced with a loud speaking unit. This device, known as a TeleTalk by the ROC allowed the observer freedom to move around in the bunker and not be constrained by the breastplate cord.

Teletalk Unit AD3460

Teletalk Unit AD3460 Click for Gallery

The TeleTalk or "Units Intercom LB AD 3460" to give its proper description is battery powered, hence LB in its description for Local Battery, utilising the same design of 6 volt dry battery [Battery, Dry No. 27] fitted in the Warning Receiver. Additionally a 67.5 volt battery [Battery, Dry No. 18] is used to send the call signal to the post display plotter. AD3460 is the diagram number, the letters AD designate a series of G.P.O. diagrams for Air Defence equipment.

There is a photograph of the Battery Dry No 18 in the gallery, it is marked as a radio battery, in days before transistor radios, this type of battery would provide the high tension for thermionic valves in a portable radio. This particular battery was manufactured in 1971.

Normally in receive mode any conversation on the cluster's omnibus line may be heard. Before speaking into the loudspeaker which acts as microphone too, a small lever switch on the right hand side of the unit must be pressed downwards. Posts within a cluster can communicate amongst themselves by voice calling. But to attract the attention of the plotter in Group HQ, the lever switch is momentarily pushed upwards to the CALL position and then released.

As posts were usually located on remote hilltops the pair of wires feeding them were often carried on poles along field boundaries making them very vulnerable to blast damage. The same wires fed both the Warning Receiver and the TeleTalk unit so both would be out of action if the line was broken.

Telephone engineers regarded these overhead lines as a bit of a joke. In the film Hole in the Ground, the featured post sent an observer out in the fallout to clear the line faults caused by the bomb exploding. This was not an easy task in peacetime yet alone a post nuclear holocaust.

Landlines within a Cluster

ROC Post Cluster Emergency Circuits

A dedicated pair of wires carried the circuit from the post to the nearest telephone exchange. The remaining part of the circuit back to Group HQ normally consisted of one or more switched lines. In peacetime these carried normal public telephone calls between telephone exchanges. For Royal Observer Corp exercises, or in time of war these circuits were switched over for ROC use. Each circuit was designated with the letters 'EC' meaning 'Emergency Circuit' and four or five digits e.g. 'EC1234'. Switchboard operators employed by the GPO / Post Office Telephones / British Telecom may recall being involved with the switching of the EC's as they were commonly known. On a post's drill night there was no way to communicate with Group HQ as switching only happened for a ROC exercise.

Switching the Emergency Circuits was a complex task when considering that York alone had Forty posts in Twelve separate clusters. This was replicated up and down the country some Twenty Five times. At each staffed switching point, firstly a 'Busy' key stopped the line being used for telephone calls, if a call was in progress on the line to be switched, a small lamp flashed until it completed. When the lamp glowed steadily, coloured pegs were moved from the 'normal' to the 'switched' position. This was fraught with problems as it was very easy to misoperate the switching. At unmanned remote exchanges, the switching clerk in the main exchange had to initiate three calls to two different telephone numbers in a set sequence and time interval.

Warning Receiver

WB400 Front View

WB400 Front View

Battery Dry No. 27

Battery Dry No.27 used in the WB400 and Teletalk

In order to receive warning of an Air Attack the Post was fitted with a Carrier Receiver. The single pair of wires used by the TeleTalk also conveyed the carrier to the Post. The operation of warning system and HANDEL are fully described in other topics on this site. Use the tabs at the top of the page to select HANDEL in the top bar, to see the topics in this category. The observers would respond to messages sent via the Carrier Receiver in the same way as any other warning point by using the hand operated siren or maroons to warn the public.

This version of receiver is power by 6 volt dry-cell battery [Battery, Dry No. 27] in the base of the unit.

The Battery Dry No.27 contains eight 'C' size cells wired as two parallel groups of four cells in series enclosed in a waxed paper box. Referring to the photograph, the number 170020, is the (GPO / Post Office Telephones / BT) Item Code number, for ordering purposes. The smaller number at the bottom 4/72, indicates this battery was manufactured in April 1972.

New batteries came with their terminals covered with a wax paper strip to prevent short circuits. The Monitoring Post kept a stock of spare batteries for use in both the receiver and TeleTalk.

Master Post Wireless Sets

ROC Post Radio ERA1

ROC Post Radio, Plessey / AT&E Countryman

Click image to see connection panel

The first trials of radio as a backup to the TeleTalk commenced in the autumn of 1961 in Winchester Group and completed in 1975 with the exception of Belfast, who had to wait for the second generation radios in the 1980's.

The wireless set shown here is an 'ATE Countryman'. Plessey purchased Automatic Telephones and Electric Co. ( ATE ) some posts radio sets may have been badged as Plessey.

Only the master post of the cluster was equipped with a single channel VHF radio allowing it to contact the Group independently of the TeleTalk landline. If it were still possible to communicate with the other posts in the cluster the master post would relay their readings to Group. Dual frequency simplex operation meant master posts could not communicate with each other. Adjacent Groups worked on different frequencies and as posts radios had only a single channel no other Group could be contacted if their own Group was disabled. These issue were addressed with the second generation radios.

The radio set was to be mounted vertically with the connections facing down. The sets were wired to a small box under the shelf which comprised of the headset socket and Push-To-Talk switch. There was no volume control as this was preset on the radio. The AF Gain control may be seen in the large photograph of the connection panel.

A detailed description Post to Group communication link using one or more hilltop repeater sites is contained on the page Communications / Networks Era 1 selected from the tabs at the top of this page.