Capacitive Relay (T1527E)

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

Controlling a blinking LED with LDR (CB24662E)
The figure shows how to control the blinking of a 5 V blinking LED with an LDR. The LED only...
Band pass amplifier (CB7447E)
Suggested by Maxim in documentation from the 90s, this circuit has its response curve given next to...
Temperature Alarm (CB6111E)
This circuit is from a 1965 General Electric publication. It uses a thermistor to fire a reed...