Found in an Electronic Design from the 90's, this circuit uses an SCR according to the controlled power. The circuit is for 12V heating elements.
This circuit can also use other series operational amplifiers such as MC33172, MC33174, MC35171,...
Found in Popular Electronics from the 90s, this circuit mutes a scanner's speaker in the absence of a...
This circuit was found in General Electric documentation from 1965. The transistors are from that...