Found in Popular Electronics of January/February 1969, this transmitter has a few meters range and can be used as a wireless microphone.
Capacitance to voltage converter (CB6075E) This Texas Instruments circuit can be used on a...
The signals from this circuit obtained from the 1965 Radio Shack documentation are picked up from...
Found in Popular Electronics from the 1980s, this circuit uses two operational amplifiers from...