HANDEL the UK Public Nuclear Attack Warning System

This description of HANDEL should be read as an introduction to the pages describing the Carrier system WB400 and its successor WB1400.

Development

The United Kingdom Warning and Monitoring Organisation (U.K.W.M.O.) was set up to give public warnings of Air Attack and fallout from nuclear weapons. The system used to convey these warnings to the public was known by the keyword HANDEL.

From WW2 until the introduction of HANDEL in the early 1960's, 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' should you be interested in the history.

The HANDEL network was installed during the early 1960ís 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 1980ís 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 Air Attack Warning message would originate from a UKWMO warning officer located at a location known variously as Strike Command (SC), Primary War HQ (PWHQ) or Air Defence Operations Centre (ADOC) If that were to become disabled, the messages could be sent from the United Kingdom Warning and Monitoring Organisation (UKWMO) Headquarters in Preston. Using the HANDEL network a verbal 'Attack Warning Red' message would be passed to control points set up in 250 major police stations. These control points would alert the public using the carrier broadcast system.

If nuclear detonations were detected by Royal Observer Corp (ROC) monitoring posts without a national attack warning being given, the UKWMO had processes in place to inform the SC/PWHQ/ADOC to enable them to retrospectively give a national warning. Also the UKWMO groups were instructed to call the carrier control points in their area and issue a local Attack Warning Red that way.

The HANDEL network utilised the existing GPO / Post Office Telephones / BT Speaking Clock distribution system.

If it were necessary to pass a warning message, the speaking clock would be disconnected causing the amplifying 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 a warning message a short burst of two tones known as P+Q tones preceded the verbal instructions. The P+Q tones triggering an alarm that sounded until a handset was lifted.

Speaking Clock

When HANDEL was first installed in 1962, the Speaking Clock or Time Signal (TIM) as it was also known 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 national warning messages around the country.

At the time of the introduction of HANDEL, the speaking clock was sourced from equipment in London and Liverpool with two duplicate clocks at each location. Each clock was a mechanical device based around multi-track magnetic recordings, replaying small sections of the time message all strung together to form a complete message every ten seconds.

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.

In 1984 these were replaced by electronic units using memory devices to store the message sections. By the time the new electronic clocks were introduced the need to change the pips at 9am. was removed as the second generation HANDEL equipment now used 1200Hz and 1440Hz for the P+Q tones.

The electronic clocks and analogue distribution network continued to serve the country after the closure of HANDEL in 1992. All remnants of the HANDEL distribution network were removed in 1994 when the analogue speaking clock rings were replaced by digital Recorded Information Distribution Equipment ( RIDE ). These racks of equipment, located in Digital Main Switching Units, were fed with a digital clock source from Network Operations Centre near Oswestry.

Fallout Warning and All Clear

If the attack failed to materialise or the raid didn't use nuclear weapons an All Clear message White may be issued at national level from SC/PWHQ/ADOC.

During and following the attack, the network of ROC monitoring posts would report details of bomb detonations and local radiation levels to their UKWMO Group HQ. The network of Group and Sector HQ's would exchange data to create a national picture of detonations and both actual and predicted fallout patterns. As fallout does not respect national boundaries the UKWMO had liaison officers in other European countries to exchange data with them.

The UK was divided into small areas of approximately 100 square miles, known as warning districts. Having predicted in which warning district fallout may settle the Group HQ would, using their direct line to the HANDEL control panel in the police station control point, ask for a fallout warning to be relayed to the Warning District's carrier receiver warning points.

After the attack and when the fallout radiation levels had returned to a safe level, probably after a period of two weeks, the All Clear would be notified by UKWMO Group controls using their direct line to the HANDEL control panel.

Police Station Control Point

HANDEL Warning Network

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 UKWMO 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 Control Point Exchange (CPE), to all the warning points. The CCP area boundary aligned closely with the telephone call charging boundary for the CPE. 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.

Carrier Control PointNumber
Braunstone066
Leicester070
Melton Mowbray071
Oakham072
Market Harborough078

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 1940ís. 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 clearly not true as the speaking clock only distributed audio voice messages.

 

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 carrier signal from the telephone exchange to the receiver. In rural areas there were no power operated sirens so receivers were located in premises such as Post Offices, Shops, Pubs, Vicarages or the homes of Police Officers, Council Officials or magistrates, who were deemed " responsible " people trusted to warn the local population by the use of hand sirens, whistles, maroons and gongs. Around 18,000 Warning Points existed nationally.

Additionally 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.

First Generation Receiver

Second Generation Speaker

In the earlier carrier receivers the instructions for the Warning Points were given on a card held in a drawer in the base of the unit. No such drawer was provided in the later receivers, but users were issued with more detailed instructions and and overview of the UKWMO structure. Both sets of instructions are reproduced on the relevant pages.