Transistorized VU (CB21729E)

The instrument of this circuit can be a common microammeter. The circuit has its operating point adjusted in the trimpot.

Geiger Detector (CB4390E)
This circuit was found in a 1962 publication. At the time there were high voltage batteries like the...
Turntable preamplifier II (CB19173E)
This preamp version uses BC109 transistors that are older versions of the current BC549 in plastic...
High Speed Optocoupler (CB23595E)
This circuit is suggested by Motorola, using a 4N26 type coupler and an MC1733 type operative. However,...