We found this micro amplifier in a technical documentation from National Semiconductor. The circuit can be used on an experimental phone, being powered even by alternative power sources.
Usiing that common diodes can oscillate, this circuit was given. The magazine that published it is...
After starting, this circuit turns off the relay in a time that depends on the 4020 pulse-count. This...
This circuit was taken from a Popular Electronics from January 1967. Transistors are from the...