We found this circuit in documentation from the 90s. Instead of a voltmeter, you can use the voltage scale of a multimeter. The circuit tests batteries under load.
Frequencies up to just over 100 kHz can be obtained with an oscillator based on one of the four...
This circuit, found in a Popular Electronics from 1992, is based on an oscillator and a crystal...
This is a discrete equivalent version of an open collector TTL gate. What we have is an inverter...