Capacitive Relay (T1527E)

Found in Popular Electronics from August 1956 this sensitive two-tube relay is powered directly from the mains power supply.

Headphone Extensions (CB23790E)
The figure shows three circuits for using headphones in amplifiers with speakers that do not have...
Nicad charger (CB9540E)
In this charger, the charging current is basically limited by the LEDs. The transformer is a low...
Fast Voltage Follower (CB4904E)
This configuration is from an old integrated circuit manual. The circuit can be applied to modern...