Door buzzer or alarm (CB20492E)

This solar powered circuit was found in a 1991 documentation. The transistor is a general purpose NPN.

Double generator (CB8943E)
Found in a 1969 Electronics World, this circuit generates low frequency signals with two...
Airflow Detector (CB6484E)
This circuit was obtained from a Popular Electronics of the 1990s. The circuit uses a temperature...
Old Push Pull Lower Power Amplifier (CB944E)
This stage was used in old audio ampliiers and radios from the 1950s and 1960s. It uses one of the...