Proportional temperature controller (CB21277E)

This circuit is from an Electronic Design from the 90's. The main integrated circuit is uncommon nowadays.

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Piezoelectric transducer driver (CB8117E)
This circuit was found in an Electronic Design from the 90s. The integrated circuit is from that...
SCR High Power Control (CB12248E)
This circuit is from a 1980 publication. In it we have a half-wave power control in which the SCR...
Microphone preamplifier (CB23705E)
We found this circuit in a Radio Electronics from February 1966. The transistor is from the time...