Micro siren (CB21234E)

This circuit with the LM3909 can be powered with voltages from 3 to 5 V. We found it in a Popular Electronics from the 90s.

Battery Charge Indicator (CB26002E)
This circuit was found in the March 1997 Electronics Now magazine. It uses a common analog...
Comparator with AND gate (CB9407E)
This tunnel diode circuit was found in American documentation from 1966. The tunnel diode is the...
Monostable with Input Lock LM339 (CB19794E)
This circuit was found in the comparator's own documentation, serving others in the same series. The...