This 1968 circuit is intended to switch the polarization of a satellite TV antenna of the time. The circuit is powered by 12 V and the transistors are from that time.
This small crystal microphone transmitter was indicated in an 80s spy book. The range depends on...
The figure shows how to use an operational amplifier with a low impedance head. The gain is...
Voltage comparators, such as those in the LM139/239/339 series, consist of devices that can be...