Voltage Monitor (CB21505E)

This fail-safe circuit was found in a 1967 Electronic Design. Transistors admit modern equivalents. The potentiometer adjusts the trigger level.

Constant Current Blinker (CB19836E)
This circuit uses the LM2931 which is not a common component today. What it does is to activate a lamp...
Frequency Doubler (CB21442E)
This circuit doubles the frequency of signals from 10 to 50 MHz. We found it in a 1969 Electronic...
4 Transistor Stereo Amplifier (CB18848E)
This circuit is from an old Japanese magazine from 1960. The circuit uses germanium transistors from the...