Phasing

Prior to the introduction of HANDEL, Air raid sirens were controlled from local police stations using GPO landlines. This early control apparatus was designated "SYSTEM E" which is also described on this web site in the topic 'Before HANDEL'.

The HANDEL network was installed during the early 1960’s and served until the end of the cold war. Following the Autumn Statement in Parliament on the 12th November 1992, the Home Office announced with immediate effect the United Kingdom Warning and Monitoring Organisation (UKWMO) would no longer function. HANDEL was decommissioned shortly after. Throughout its life the equipment was installed and maintained by what was the GPO, then became Post Office Telephones and finally British Telecom.

The initial HANDEL system had two integrated parts, the WB400 speech broadcast system and the WB600 siren control system. Confusingly both used the same 72kHz Carrier system and were actually both integral parts of one system. A full description of this equipment is given in subsequent topics.

During the early 1980’s the original equipment was replaced by the new WB1400 system using more modern technology and addressing the shortcomings of the previous one. It continued to use the same carrier frequency so the two could work together during the changeover period. A full description of each system may be found in this section by clicking the Tabs at the top of this page.

National Attack Warning Red

The decision to issue a National Attack Warning Red would be made at Strike Command at RAF High Wycombe or UKWMO Headquarters at ROC Preston. Using the HANDEL network a verbal message would be passed to control points set up in 250 major police stations.

The HANDEL network utilised the existing GPO / Post Office Telephones / BT Speaking Clock distribution system. The Speaking Clock was distributed on a duplicated circle of lines between major telephones exchanges designed to raise an alarm if the ring failed. This provided a ready made and secure (against breakdown) system of distributing the attack message around the country. At the time of the introduction of HANDEL, the speaking clock was sourced from equipment in London and Liverpool. The clock was a mechanical device based around multi-track magnetic recordings, playing back small sections of the time message all strung together to form a complete message every ten seconds. There were two machines providing the clock messages at each site. In 1984 these were replaced by devices using digital memory to store the message sections. These continued to serve the country after the closure of HANDEL. During 1994 the analogue speaking clock rings were replaced by Recorded Information Distribution Equipment ( RIDE ) in Digital Main Switching Units fed with a digital source from Network Operations Centre near Oswestry.

The speaking clock would be disconnected before an attack warning message was passed. The removal of the clock announcement causing the equipment in the telephone exchange to connect Number Unobtainable Tone to the public feed of the speaking clock and prevent any call charges being raised.

To alert the Police Station Carrier Control Points to an incoming attack warning message a short burst of two tones known as P+Q tones preceded the verbal instructions. In the first generation of HANDEL, the P+Q tones were of 2400Hz and 2600Hz. For engineering test purposes the three pips of the speaking clock changed from their usual 900Hz tone to 2500Hz at Nine O'Clock precisely every morning. The 2500Hz tone chosen to be midway between the P + Q tones. The second generation HANDEL equipment changed the P+Q tones used to 1200Hz and 1440Hz so by the time the electronic clocks were introduced in 1984 the need to change the pips at 9am. was removed.

At the time I worked on the system (1978-1981), the location of Strike Command was unknown to me, so I have no idea how the warning message was injected into the Speaking Clock distribution system.

Fallout Warning and All Clear

Royal Observer Corp. (ROC) Observer Posts would report details of bomb detonations and local radiation levels to the ROC Group HQ. The network of ROC Group HQ would exchange data to create a national picture of detonations and fallout. As fallout does not respect national boundaries the UKWMO had liaison officers in other European countries to exchange data with them.

Having predicted in which Warning District fallout would occur the ROC Group HQ would, using their direct line to the HANDEL control panel in the police station control point, ask for a Fallout Warning or subsequent All Clear message to be relayed to the Warning District.

Police Station Control Point

The UK was divided into 250 Carrier Control Points located in a major police station. Each control point would issue warnings to one or more warning districts. The control unit had duplicate HANDEL handsets to receive the attack message. During peacetime the speaking clock could be heard on these handsets. A third HANDEL handset connected to the ROC Group Headquarters for that Warning District would be used to receive any Fallout Warning messages and eventually the All Clear.

HANDEL is a two stage system. Onward distribution of public warnings required human intervention at the police station to retransmit the message. Neither Strike Command nor the ROC had any direct way of alerting the end user at the warning point. The police station control panel could be used to issue verbal messages and activate electric mains operated sirens.

At the Police Station, a 72 kHz carrier, modulated with speech or tone signals was generated in the Carrier Control Point (CCP) equipment. This was distributed via the main telephone exchange, known as the Carrier Control Exchange (CCE), to all the warning points. The CCP area boundary aligned closely with the telephone call charging boundary for the CCE. To provide security against a fault going unnoticed, carrier system was used to distribute the Police messages and siren control signals, using existing telephone lines. This helped detect faults in the carrier system and saved the cost of providing extra wires often to remote locations. If the wires became disconnected the telephone would be reported faulty, long before the carrier system was next tested. Filters separated the audio from the carrier so both the telephone and receiver could be used simultaneously.

Control Point	Number
Braunstone	066
Leicester	070
Melton Mowbray	071
Oakham	072
Market Harborough	078

Copper pairs between the exchange and customers premises are able to carry signals well above the range of human speech. This extra bandwidth may be used to carry signals without interfering with the normal telephone operation. ADSL used to provide Broadband Internet is a modern system using this same bandwidth. However other simpler systems known as "Wire Broadcast" (WB) have been around since the 1940’s. A paper read to The Institute of Post Office Electrical Engineers on the 11th April 1949, describes the trial of a multichannel carrier system for broadcasting BBC radio programs over telephone lines.

It has been wrongly reported in the past that the 72kHz carrier was broadcast over the Speaking Clock system. Such as - RSGB RadCom July 2001 The Voices page 35. This myth may be found in the chatter on the uk.rec.subterranea news group too. From the diagram you can see this is not true. The speaking clock only distributed audio.

 

Public Warning

In built up areas mains power operated sirens would be operated by signals sent from the CCP. These were often WW2 siren locations in addition to the receiver they had a control panel to allow local activation. During peacetime the fuses to the siren motor were removed to prevent accidental operation.

The warning receiver is the part of the system most visible to the general public. The normal telephone line at the premises carried the signal from the telephone exchange to the receiver. In rural areas there were no power operated sirens so receivers were located in premises of " responsible " people such as Post Offices, Shops, Pubs, Vicarages or the homes of Police Officers, Council Officials or magistrates. The ROC posts acted as warning points too. The receiver would relay the Police messages for attack and fallout warnings, the owner would warn the local people by the use of hand sirens, whistles, maroons and gongs. Around 18,000 Warning Points existed nationally.

A warning receiver was likely to be found on the premises of about 4,000 Warning Recipients who would need to know if it were safe to go outside. These would be Fire Stations, Police Stations, Hospitals, Public Utilities and Feeding stations to name a few.

In the earlier carrier receivers the instructions for the Warning Recipients were given on a card held in a drawer in the base of the unit. The card is reproduced above.