Two-tone solar buzzer (CB20493E)

This circuit was found in a 1991 publication. The transistor can be a general-purpose type.

20 minute timer with PUT (CB4254E)
This circuit was found in the ON Semiconductor's Thyristor manual of the 1980s. The high quality...
Pulse Width to Capacitance Converter (CB6100E)
Suggested by Linear Technology, this 80's circuit makes use of an operational of the time but can...
Active Cycle Detector (CB6529E)
This circuit was obtained from a Popular Electronics of the 80's. It is set to a certain pulse...