Two designs of hand siren were employed at UKWMO Warning Points during the Cold War period. Both designs are shown below along with the user instructions on how to sound the Attack Warning and All Clear.
Carter Hand Siren
The two models of hand siren are of a similar design but not quite the same. The easiest way to distinguish them apart is by their frame. The Carter Siren has an angle iron frame.
Both makes of siren have a top steadying handle incorporating a twist grip. The grip controls the opening and closing of shutters over the air inlets.
Secomak Hand Siren
I am grateful to Paul Lawrence for these photographs showing the packing arrangement for the Seckomak. The rubber ring on the top handle holds the winding handle in place when packed.
Sounding the Siren Instructions
Red Warning (Attack)
(1) Ensure that the damping shutter on the sound box is in the "open" position and that it remains open for the duration of the signal. (The open and shut positions of the damping shutter are controlled by a twist of the steadying handle on the top of the siren).
(2) With one hand grasping the rotating handle and the other holding the steadying handle, give the rotating handle five revolutions at a very fast speed by continuously increasing the pressure on the handle. (It is difficult to define "very fast", but the object will be to turn the handle for these five revolutions as quickly as possible).
(3) After these five revolutions have been given, drop the rate of turning to a slow speed by decreasing the pressure on the handle for the next five revolutions. (the "slow speed" rate of turning need be no greater than the speed at which the handle would rotate by itself from the momentum resulting from the previous five turns).
(4) Then give another five turns at high speed, followed by five turns at slow speed, and so on. This sequence should be followed for ONE MINUTE and it is important that this timing is strictly maintained since it is one of the distinguishing features of the signal. It is also most important that there should not be any variation of the five in number revolutions of the rotating handle during which the pressure is successively built up and then reduced. The resultant noise from the siren would be the wailing note with which many persons are familiar.
White Warning (All Clear)
(1) Ensure that the damping shutter is open and remains open for the duration of the signal.
(2) With one hand grasping the rotating handle and the other hand holding the steadying handle, rotate the handle at the highest rate it is possible to maintain for the whole of ONE MINUTE during which the speed must remain constant in order to sustain the note at a level pitch. Here again, the duration of the signal is an important distinguishing feature. The resultant noise should be the long steady note with which the public are also familiar.
In the nineteen fifties, it was planned to sound the grey warning to say that fallout was expected but not for one hour, giving citizens the opportunity to make last minute preparations. The idea was abandoned by the nineteen sixties and the facility was not incorporated into the newly developed carrier warning system WB600.
The Grey warning signal would last for two and a half minutes, with the siren turning at a constant speed, the operator would twist the grip handle to open the shutter for five revolutions of the winding handle and close it for the next five, this sequence was to be repeated continually for the duration of the signal.