Home Office Type 447 Hand-Operated Siren
This hand-operated siren (sometimes spelled 'syren') was intended for large or remote establishments such as R.A.F. airfields and large factories where the public air raid warning may not have reached.
The siren consists of a simple bladed drum (shown left) rotated through the use of the handle. The blades are angled so that air is drawn in through the holes in the voicebox casing, and forced out the side to produce a howling tone. In order to produce the fluctuating 'Action Warning' signal, the user let go of the handle and let the siren slow down before cranking up again to reach the high note.
There appears to be very little documentation charting the history of the Type 447, but it would seem to originate in the late 1930's. Protection Against Gas in the Field mentions a "hand-operated syren, which can be heard over a fairly wide area is issued for the general alarm down to headquarters of companies and equivalent units." [1] It may be that the Type 447 was developed from this.
These small sirens were manufactured by 'Secomak' (later 'Klaxon') and a similar design with a triangular stand was produced by another firm, Carter. They were essentially a smaller version of the large motorised sirens used in urban areas. These were often driven by a 4-5 horsepower motor and consisted of two rotary voiceboxes of different size to produce a more harmonious note.
This particular siren was manufactured by Secomak, and the handle is stamped 'AM 5/40' probably signifying that it was owned by the Air Ministry, and received in May 1940.
For long-term storage, the siren assembly could be removed from the stand and re-attached upside-down to save space.
Gas Rattle
The rattle had originally been used as a gas alarm in the trenches of the First World War and had developed little by 1939.
There were slight variations though; some rattles had twin slats and others had 'sounding boxes' fitted to make them louder.
The rattle was an ideal alarm; it sounded like nothing else and had a piecing noise that was not easily drowned out except by the loudest background noise. A key advantage was that, unlike a whistle, it could be used when wearing a respirator.
Hand Bell
The hand bell was intended to be rung to sound the 'All Clear' signal, and this causes confusion with the 'Raiders Passed' signal. The latter was sounded on the siren as a continuous steady note, and signified that enemy aircraft were not threatening that particular district.
According to Air Raid Precaution Handbook No.8, The Duties of Air Raid Wardens:
"The cancellation of the local gas warning will be by hand bells, rung through the streets of the [warden's] sector. Hand bells may also be used to repeat the Raiders Passed signal but only if gas is not about. Hand bells will in fact be an "All Clear" signal, which is different from the Raiders Passed signal, since the latter will be sounded on receipt of the message from the national centre, whether or not there is gas in the locality." [2]
Therefore, the 'All Clear' meant that there was no danger from either enemy aircraft or poison gas. However, in October 1939, the London Civil Defence Region issued a circular [3] ordering its wardens to use hand bells only to cancel a gas warning (rattle) that had previously been given and not to reinforce the 'Raiders Passed' signal when the gas rattles hadn't been sounded, to avoid confusion.
The circular caused a stir with higher authority, who could see the sense in London's proposal, but could not easily revise the advice that had been printed in thousands of copies of Handbook No.8!
It is not certain whether the issue was ever adequately resolved, but in September 1940, the Ministry of Home Security ruled that hand bells could be used to sound 'Raiders Passed' if the local authority believed that a significant number of people had taken shelter during aerial action that had not been signalled with the 'Action Warning' on the sirens. [4]
A.R.P. Whistle
These whistles, manufactured by J. Hudson & Co. of Birmingham were issued to every warden after the Home Office had pestered the Treasury to provide one per person for reasons of hygiene. The unsympathetic response was that "if blowing somebody else's whistle is the least convenient or unhealthy thing wardens have to do in war they will not have fared too badly." [5] However, it was finally agreed to issue every warden with a whistle and allow them to carry them at all times during war.
According to Air Raid Precaution Handbook No.8, The Duties of Air Raid Wardens:
"The Action Warning can be reinforced by wardens by sharp blasts on a whistle. These should not be continued after the public appear to have heard the warning, or they may cause undue alarm. But whistle blasts can be used by a warden to signal to anyone out of doors and appears to ignore the warning." [6]
The whistle was later used by Fire Guards to signal the fall of incendiary bombs with a series of sharp blasts. [7]
References
- War Office, Protection Against Gas and Air Raids 1939. p54-55
- Air Raid Precaution Handbook No.8, The Duties of Air Raid Wardens 1939. p16
- London Civil Defence Region Circular No.77 22 October 1939 HO 186/250
- PRO HO 186/250
- Treasury to the Home Office, 1 June 1939 HO 186/1788
- The Duties of Air Raid Wardens op. cit. p15
- Air Raid Precautions Handbook No.14 1942. p5