Diode Tester (CB22137E)

This diode tester was found in an English publication from the 1980s. Transistors are general-purpose types of the time.

Relaxation with Operational (CB15020E)
Any operational amplifier, like the 741, can be used on this oscillator whose frequency depends on R1...
Variable High Q Filter with the 741 (CB13604E)
This circuit was found in a 1973 publication. With the components indicated, the range can be from...
Ice Alert and Lights On (CB4965E)
This circuit for vehicular use is from an 80's American publication. The circuit has a light...