The Microphone. A special microphone, the D 102 Mi, was developed by the firm of Hasag, Leipzig, for use with the DA 102. It is a carbon button type microphone mounted on a diaphragm at the bottom of a D 102 mechanism. In order to accomodate this micro-phone, the D 102 is modified in the following manner:

1. The internal diaphragm is removed.

2. The bottom plate is replaced by a special disc. This disc has a hole in its center which houses a thin, rubber-covered, metal diaphragm. The microphone button is moun-ted on the inner side of the diaphragm.

3. The anti-detonation valve is removed.

The microphone button is fitted with a small leak-holse leading from the inside of the microphone pot to the carbon granule chamber. By this arrangement, the microphone diaphragm is exposed to the water, but, since the hydrostatic pressure is equalized by compression of the air within the rubber bag, there is no loading of the carbin granules and the sensitivity of the microphone remains unaffected.

Ths microphone is highly sensitive and has an essentially flat response for both sonic and subsonic frequencies. The sonic frequencies are transmitted to the carbon button by the diaphragm, and the subsonic frequencies by the rubber bag.

Figure 241 – AD 105a Unit with D 102

Figure 246 – LMB/S Tail