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.

LM383 8 W Amplifier (CB17532E)
The integrated circuit used in this 1986 project is not very common today. The circuit uses few...
4 W amplifier (CB12871E)
This is the circuit of an old commercial amplifier from Fapesa (Philips Argentina) from the 1970s....
Touch Bistable (CB15005E)
Alternating taps on the pressure switch or sensor, cause the output to alternate the high and low...