Null indicator (CB22313E)

This circuit for measuring bridges was found in American documentation from the 60's. Transistors are germanium types of the time.

Touch Alarm (CB9887E)
We found this circuit in a 1979s British publication. The circuit can be assembled with more...
CMOS Digital Frequency Meter (CB4646E)
This simple digital frequency meter using CMOS circuits reaches 5 MHz frequency. Input signals are...
ISD1016 Voice Recorder (CB25448E)
This 16-second voice recording circuit was featured in a telephone answering machine circuit in...