British Army and Civilian Respirator Microphones 1935-45  General Service Respirators Mk.IV and Mk.VThe Mk.IV General Service Respirator facepiece had no provision for mounting a microphone for use with radio sets or telephones until the introduction of the Special T Mic. facepiece (see photo at right) in the 1930's.  The Special T Mic. had a rubber turret moulded onto the left cheek of the facepiece to allow a microphone to be mounted. Until a microphone was fitted, the turret was sealed by inserting a plastic plug into it, and clamping it in place (see photo at left). The plug was then simply removed and the microphone inserted and clamped. The introduction in 1937 of the Special Service (later Civilian Duty) Respirator for Air Raid Wardens and other Civil Defence personnel highlighted the need for a microphone facility to be available for those manning telephone switchboards, and the general inconvenience and production problems of producing special facepieces led to the S.S. Respirator being produced with the Special T Mic's microphone turret moulded as standard. The new Mk.V General Service Respirator was similarly equipped when introduced the following year. 
Microphone, Respirator, No.1 and No.2There were two main types of respirator microphone used by the British Army; No.1 was intended for use with radio sets in the field, and was fitted with a long (120cm) wander lead and plug. No.2 had a recessed two-pin socket into which a shorter lead from a static set (such as a switchboard) was plugged into. Similar in general size and appearence, and housed inside a black bakelite casing, there was probably little or no internal difference between the two types. Both probably remained in use as long as the General Service Respirator. Microphone, Respirator, No.3 was developed during the late 1950's for use with what was to become the S6 Respirator.
Respirator, Anti-Gas, LightThe Light Respirator required a different method of microphone use from the General Service Respirators; as the container mount was situated on the left cheek, the microphone turret had to be omitted from the design. (Fitting the microphone on the right cheek would have interfered with weapons handling.) 
As the Light Respirator had better speech quality due to its larger voicemitter membrane, it was found that using a standard microphone (Microphone, Hand, No.7, seen here) intelligible (90% clarity) speech was possible over a radio net, even when speaking from inside a tank on the move. The only modification required was to roll the rubber speech trumpet on the microphone back on itself to get the microphone closer to the respirator's speech diaphragm. There were several designs of outlet valve cover for the Light Respirator, each progressively more compatible with the No.7 Microphone. The L5 outlet valve of the mid-1950's (seen left) had its origins in the L2 type first seen in 1943, and patented the following year. 
The Respirator TelephoneIt is not clear where the microphone used with the civilian Respirator Telephone fits into the general scheme, but as it was designed for use with civilian telephones and exchanges, (the plug jack is larger than that of the army types) it would appear to be unrelated to them. The capsule employed with the Respirator Telephone was quite bulky and heavy, but as the operator was intended to be stationed constantly at a switchboard and not moving around, these problems were of secondary concern. However, if the army's Respirator Microphones had been compatible with civilian exchanges, it would have made sense to have issued them instead. For more information on the Respirator Telephone, see the British Respirators page. References
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