Variable regulator with crowbar protection (CB21189E)

This circuit was found in a Popular Electronics from the 90's. The power transistors must be equipped with a heat sink.

Triangular Oscillator (CB18943E)
This circuit generates a linear triangular signal whose frequency is determined by C1. Transistors...
T Bridge Audio Oscillator (CB4689E)
This circuit is from an ancient American documentation. The T-Bridge circuit determines the...
TTL Flasher 7400 (CB479)
Two LEDs are used in this TTL circuit. Frequency is given by C1 and C2. Power supply must be a 5 V...