Gagarin's microphone DEMSh
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Since I once worked on the railroad, I took this DEMSh-1A from a travel radio station. The microphone body has a diamond shape molded into the side.
The DEMSh (differential electromagnetic compact noise-resistant) microphone is a professional device designed for use in communications equipment, including telephones, sound reinforcement systems, and marine communications. It is designed for use in extreme conditions, including tropical climates.
The DEMSh is designed as a symmetrical electromagnetic system with a diaphragm open on both sides. When the sound pressure on either side of the membrane is uneven, it oscillates in time with the change in sound pressure. Because the microphone is small, the sound pressure at both ends differs significantly only when the sound source is close and asymmetrical relative to the diaphragm. At significant distances from the sound source, vibrations are ineffective, even at high sound pressure levels. This is why the microphone delivers a high-quality output signal, significantly attenuating various types of noise from the transmission site.