The Warning Messages

It was planned to advise the public of the onset of attack, subsequent fallout and all clear by issuing three colour coded messages -- Attack Warning RED, Fallout Warning BLACK and Attack Message WHITE. During the build up to an attack the public were to be advised what to do when hearing the warning. The infamous Protect and Survive videos and booklets were part of this advice. Television stations were expected to broadcast the advice videos.

• The Attack Warning RED was to be signalled with siren sounding a rising and falling note.
• The Fallout Warning BLACK would be given in a number of ways. Three exploding maroons, three blasts of a police whistle or three bangs of a gong.
• The All Clear, called the Attack Message White would be a 30 second continuous sounding of the siren.

Getting the Message Across

The Air Attack Warning message from Strike Command or the United Kingdom Warning and Monitoring Organisation (UKWMO) Headquarters would be passed to police station control points via the HANDEL network. The HANDEL network utilised the existing Post Office Telephones (later became BT) Speaking Clock distribution system.

The UK was divided into 250 areas each with a control point located in a major police station. The police station control unit had duplicate HANDEL handsets to receive the attack message. A third HANDEL handset would receive any Fallout Warning messages and eventually the All Clear from the Royal Observer Corp. (ROC) Group Headquarters for that area. The siting of the control point in a major police station was a continuation of the role of the police in warning the public of air raids that was started in WW2.

HANDEL is a two stage system requiring intervention at the police control to pass the message on. The officer in the police station control would then issue appropriate verbal messages and activate electric mains operated sirens. These spoken messages or siren commands modulated a high frequency carrier signal. The carrier was distributed via the main telephone exchange to all the warning points in the area. To provide security against a fault going unnoticed, the carrier was sent over lines used for normal telephony.

At the warning points a signalling receiver would control the operation of the mains powered siren. These were mainly found in towns and cities but in rural areas the warning would be given with a hand operated siren. Warning points in rural areas were fitted with a speech receiver. The owner of a speech receiver would hear the spoken message from the control point and be expected to warn the general public by hand cranking a siren kept on their premises. People deemed as responsible were chosen to accommodate speech receiver and siren, such as shop keepers, publicans, council officials, vicars, post masters or the local bobby in a police house.