The Emergency Manual Switchboard System - E.M.S.S.

The Emergency Manual Switchboard System was designed to provide a skeleton long distance telephone service for Civil Defence, Military and Emergency Services should the normal network be affected by enemy action. The system was removed at the end of the cold war in the early 1990's.

The U.K. Analogue Telephone Network

In the Nineteen Sixties the UK telecomms infrastructure was run by the GPO / Post Office Telephones and very different from today's British Telecom digital networks. There was no competition from operators in the market such as Mercury, Sky, TalkTalk or Virgin, as there is today. Less than a quarter of people had a telephone in their own home. Due to the lack of government investment in the telephone network, there was often a waiting list for a telephone, residential customers may have had to share a line, with no privacy between them. Unbelievably, there were advertisements to discourage calls at certain times of the day and encourage users to keep the calls to a short duration.

Most local calls (classified as within a radius of 20 miles) could be dialled directly. Automatic long distance dialling known as Subscriber Trunk Dialling (STD) was introduced at Bristol in 1958. The national rollout took in the region of 20 years. So by 1962 other than in the main cities, customers wanting a call over 20 miles dialled '100' for the operator who then connected the call.

Major towns had an automatic telephone exchange known as a Group Switching Centre (GSC). This exchange switched customer dialled calls for the local area. Often there would be a co-located Auto-Manual Centre (AMC) housing operator switchboard positions handling long distance calls, directory enquiry and 999 calls for the local area. The EMSS switchboards were located at an AMC to provide switchboard operators to staff it.

During the Nineteen Seventies, home telephones gradually became more common, so by the Eighties the majority of homes had one. By the end of the Seventies, all long distance and most international calls could be dialled directly, without having to go via an operator. Analogue mobile telephones only started to appear in the early Nineties just as the Cold War was ending, but the high price of handsets and calls restricted them to business people.


Telephone Network Overload

All telephone networks are very susceptible to overloading caused by a local or national event, this can be anything from bad weather to a radio phone-in. The networks are only designed to cope with average number of calls. With today's modern digital networks, calls can be rerouted to avoid local problems. During the Cold War period the analogue network didn't have this resilience.

It was assumed overloading would occur during the period of build up to war as people tried to call relatives. Damage caused by war action itself would severely disrupt the network. To prevent overloading affecting essential services and the war effort, a system of disconnecting less essential telephones was introduced in the analogue network, which has been carried forward into the digital and mobile networks too. The disconnection facility is known as the Government Telephone Preference Scheme (GTPS).

This may sound harsh but in the sixties and seventies the network often could not cope with normal traffic and engaged tone was very common. In a war situation it was unlikely to cope with the predicted surge of calls, so by invoking the GTPS, the capacity could be reserved for government, military and civil defence lines

Even as network capacity increased to present day standards, voting for a reality television show can easily overwhelm it. In the present day digital network an additional software tool known as call gapping is used to reduce the peaks of calls to voting or other specific number(s). This wouldn't work in an emergency situation where calls are made to friends and family but not a specific number. The GTPS still exists in the landline network and a similar arrangement, the Mobile Telephone Privileged Access Scheme (MTPAS) is in place on the mobile phone network. They may be used if we suffer a terrorist attack or a natural disaster such as flooding or earthquake jeopardises the telephone network.


Government Telephone Preference Scheme

This scheme works by separating telephone lines into three preference category groups (Pref Cat).

The first stage of disconnection prevents Category 3 customers from making calls. The second stage of disconnection prevents both Category 2 & 3 lines from making calls. The Category 1 lines have no disconnection facility. All lines regardless of their category can receive incoming calls. So even with the maximum level of disconnection enabled, a Category 1 line would function normally as they could still make a call to a Category 1, 2 or 3 line.

Within each GPO Telephone area, a small group of employees in the 'Area War Group' (AWG) liaised with government and the military to maintain a list of lines in Pref Cat I & Pref Cat II. When these lists changed, engineers were instructed to take action to modify the customers exchange line in the exchange.


The Emergency Manual Switching System (EMSS)

Manual Switchboard

The EMSS was a network of 300 manually operated switchboards that would only be activated in war. It would be used during the transition to war, if normal operator service were suspended. There was an option to handle the EMSS calls on the 'Normal' peacetime switchboard or divert the calls to small 'Emergency' switchboard protected from blast and radiation. In the Post-Strike phase it would operate from the protected accommodation providing service to essential users during the recovery phase

Many essential locations were connected directly to their nearest EMSS switchboard, these include all UKWMO Group Headquarters, Regional Government Headquarters, Council emergency centres (Main and Standby). Each Armed Forces Headquarters (AFHQ) was connected to two different EMSS.

This picture shows the type of switchboard used for EMSS. There are three operator positions in this example, each handling up to nine calls. Calls were connected using plugs on the ends of cords. At Kettering exchange, where I worked in 1976 there were two groups of ex-directory numbers designated 'Civilian' and 'Military' priority answer, known as PRT(C) & PRT(M) respectively.

There were dedicated bothway lines to Leamington Spa EMSS, Leicester EMSS, Leicester telephone area War Group and Peterborough EMSS. These were exclusively for emergency use and not for day to day traffic. The essential location (listed in the paragraph above) directly connected external lines, were known as 'Trunk Subs' These get their name from, 'Trunk' is a line between switchboards and 'Subs' the abbreviation for 'Subscriber' the word for 'Customers' back then.

I have received correspondence from a person working at a UKWMO HQ switchboard, who plugged in to the EMSS line and received an answer, most likely from the 'Normal' switchboard.

The 1960's EMSS room in the basement of Kettering sorting office contained ration packs and beds, but the toilets shared with the postmen were down a corridor, there was no strengthening or blast door. Suitably protected accommodation was provided when the automanual centre and EMSS moved across into the current purpose built telephone exchange building, built in the late seventies.


Service Provided

EMSS Network

I can only speculate on the service the EMSS would provide. Nobody locally appeared to have any instructions but it was assumed the Area War Group (AWG) would issue these if the need arose. Regular speaking and calling tests were performed with the circuits switched to both the 'Normal' and 'Emergency' switchboard.

In the sixties, seventies and early eighties Post Office Telephones / British Telecom was organised into telephone areas and regions. The Leicester telephone area of which my exchange at Kettering was a part had its Area War Group (AWG) in Leicester Free Lane exchange. The function of the AWG was to co-ordinate the emergency response. AWG switchboards had links to other areas and the Regional War Group in the Regional Headquarters in Birmingham.

In the run up to war the appropriate 'Military' or 'Civilian' ex-directory number would be issued to people or organisations allowed to use the EMSS service, but without directly connected 'Trunk Subs'. Additionally the users would have Category 1 preference on their telephone lines so they could still make calls if service was removed from non essential lines. These ex-directory numbers were given priority (PRT) over normal code 100 operator calls when the 'Normal' switchboard was being used. the switchboard calling lamp white Opals were marked with a 'P'.

Corsham Bunker to E.M.S.S.

Calls from the ex-directory PRT(C) or PRT(C) or from 'Trunk Subs' would be answered by the EMSS operator and extended around the network using only the reserved lines between EMSS switchboards to their final destination. The destination switchboard could call the 'Trunk Sub' and connect the call, or dial out to a local number over the PRT line.

De-classification of documents relating to the Central Government's Emergency War Headquarters (CGEWHQ) at Corsham, reveal that in 1968 it had a total of 37 lines to EMSS switchboards around the country. On the map, Corsham is the Red dot and the E.M.S.S. locations are shown in Green.

EMSS        Lines  |    EMSS        Lines
Reading     10     |    Carmarthen  2
Worcester   10     |    Exeter      2
Bath         3     |    Lancaster   2
Salisbury    3     |    Perth       2
Taunton      3     |

Corsham was a very well kept secret, so it would be interesting to know how the lines were marked on the EMSS switchboards listed here to avoid giving away the existence or location of CGEWHQ. Perhaps simply by using its 1141 code 'QQCF'.



The EMSS network and switchboards closed in the early nineties at the end of the cold war. The GTPS and post cold war ACCOLC for mobile phones still exist and are likely to continue in one form or another. This should not been seen as anything sinister. In the past it has been necessary to use the GTPS when telecommunication equipment has been accidentally damaged to ensure the emergency services can still function.

At the time of the Electricity Generator workers' industrial dispute in the early 1970's I recall working by battery lights during a power cut to match the correct level of Preference category for emergency lines, compared with the list provided by the AWG. However it was never necessary to use the Preference Scheme in Kettering as our emergency generator never failed.