Motorcycle headlight monitor (CB9117E)

This simple circuit was found in Popular Electronics from the 1980s. The circuit uses an LED as an indicator.

JFET AM radio (CB22038E)
This receiver with two common JFETs was found in an old English documentation. The phone is...
Binary counter (CB22437E)
This TTL circuit with the 7493 makes the binary count of the pulses sent by a flip-flop with the...
Long interval timer (CB9365E)
This circuit was found in a Popular Electronics from the 90s. The counter circuit is not common...