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 for link or alarm was found in the Encyclopedia of Electronic Circuits Volume 5 of...
This small experimental transmitter can send its signals to distances up to 100 meters. L is...
In the figure we have the way to use an on-off sensor to control a load up to 100 mA. The circuit has...