RAF type 20/21 microphone with scarce antifreeze cap

RAF, type 20/21 microphone and scarce anti-freeze metal gauze cover.

Type 20/21 microphone Ref No. 10A/11994 (10A/11993) is in a very good condition with some minor paint loss. This type of microphone was used in conjunction with the type-D cloth oxygen mask.

It comes with the cover, gauze, antifreezing type 3, Air Ministry Ref. No. 10A/12924.

This rare piece of kit was developed to cover the microphone bakelite disc. At low temperatures it was found that the airman's breath formed ice, which covered the small sound holes in the bakelite disc, and this stopped the microphone from working correctly. RAF, A.P.1186 manual states that 'when fitted with the gauze cover, ice formation will then be prevented by covering the surface of the gauze with a thin layer of anti-freeze oil, type A'. This type of cover later became obsolete with the introduction of heated microphone covers. The cover is in excellent used condition.