GEC BCS 2285

A small dynamic microphone with aerodynamic styling, made in England under the GEC brand.

The microphone is covered by British patent number GB432717A, which is dated 1st February 1935 and was filed by Donald McMillan of North Harrow in Middlesex. Interestingly the patent was not filed by GEC, so perhaps they licensed or bought the intellection property from the inventor. The patent claims the following:

1. A moving coil microphone, wherein the diaphragm is of such a construction as to be capable of comples modes of vibration at high frequencies in the audio range so that the sensitivity is reinforced at these high frequencies, the diaphragm being inertia controlled and a free air path for sound being provided to both the front and the back of the diaphragm to compensate at low audio-frequencies for the decrease of the velocity of the coil with the increase of the frequency due to the inertia control.
2. A microphone in accordance with Claim 1, wherein the length of the said free air path is so related to the mechanical characteristics of the diaphragm that an approximately uniform frequency characteristic is obtained.
3. A microphone in accordance with Claim 2, wherein the adjustment of the length of the free air path is effected by providing a baffle of suitable size.
4. A microphone in accordance with any preceding claim, wherein the diar phragm comprises a paper cone.
5. A moving coil microphone arranged, constructed and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.