Found in American documentation from the 1980s, this circuit has a diode feedback. At the exit we have an indicator LED. The LM3900 is a transconductance operational amplifier.
This circuit was found in a 1974 publication. It provides a tone indication of the temperature sensed by...
This is a simple rheostat circuit for motor control that works with voltages from 6 to 12 V. The...
This circuit with TTL compatible output was found in a 1968 US documentation. The circuit is...