Motorcycle headlight monitor (CB9117E)

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

Active Antenna (CB4750E)
This good gain antenna up to 30 MHz was found in an American 1990s documentation. The circuit can be...
Frequency to voltage converter (CB6032E)
This converter can be used to send information remotely from linear transducers, converting voltages...
741 Timer Up To 10 Minutes (CB1270E)
This timer with 1 second accuracy was obtained in a 1973 documentation. The Buzzer is a low-power type...