Digital recorder ISD1016 (CB7963E)

Found in a Popular Electronics from the 90s, this digital recording circuit uses an unusual integrated circuit today.

Instrumentation AC Amplifier (CB12502E)
This circuit increases the sensitivity of a multimeter in the measure of small alternating...
Intrusion Alarm (CB26238E)
This circuit triggers a buzzer or other warning device when the light falling on the sensor is cut...
Pulse Generator (CB883E)
This circuit open and close the relay in intervals adjusted by the potentiometers. The capacitors...