Motorcycle headlight monitor (CB9117E)

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

RS232 temperature interface (CB21278E)
Found in an Electronic Design from the 90's, this circuit uses common components. The circuit is...
Locked Light Relay (CB3868E)
When the sensor receives light, the relay closes its contacts and remains so even after the light...
90V Pulser (CB8838E)
This circuit produces pulses of 90 V at intervals that can reach 5 minutes. The circuit is from a...