We found this version of the automotive tachometer in a 1980s publication. Variations from other sources appear elsewhere in this section. The indicator is a 0 to 1 mA milliammeter.
This circuit can be powered by 2 or 3 small batteries. The resistor can have values between 220...
This traditional configuration with the 555 was obtained in an 80s Hands-On Electronics. The relay...
Found in American documentation from the 1980s, this circuit shows how to use an LM3909 pulsator in a...