This transmitter for the 3.5 and 7 MHz ham radio was found in a 1950s Japan publication. No information was given on the coils and the power supply.
This series sensor circuit is from 1995 Popular Electronics. The circuit can use any SCR and the...
The circuit is a multivibrator version using two NPN general purpose transistor. This circuit can...
This circuit is from 1976 documentation. It uses the operational amplifier 709 which is no longer...