Capsule microphone and telephone receiver.

Everything else not included in the sectionsInterphone devicesCapsule microphone and telephone receiver since 1965 (possibly earlier) were produced by the Moscow plant No. 4 "Fizelektropribor". The kit is a tutorial for demonstrating the conversion of sound vibrations into electrical (carbon microphone + battery) and, conversely, electrical vibrations into sound vibrations in a telephone receiver, with the microphone and telephone receiver being spaced over a distance using wires.