Low battery indicator 555 (CB9551E)

This circuit can operate with different voltages, depending on the zener used. We found it in a 90s American documentation.

Magnetic capsule preamplifier (CB7102E)
This circuit was found in a Popular Electronics from the 90s. The circuit uses general purpose...
Micro Injector (CB21911E)
Found in Raytheon's 1960s transistor circuit manual, this circuit employs the CK722, one of the...
Residential Lock and Alarm (CB18669E)
This encoded lock circuit with alarm for use in homes was found in a publication from the 90s. The...