This circuit was found in 80's telecom documentation. Its purpose is to control a microphone in the process of transmitting voice and Morse signals.
The presented circuit simulates a high power zener that depends on the characteristics of the...
The oscillator shown in the figure generates a 1 kHz tone that is reproduced on the speaker with...
This circuit, suggested by Texas Instruments, uses a TIS43 or 2N2646 to produce short light pules. The...