For low-frequency signals, this circuit transforms a single oscilloscope into a dual-trace. The circuit is from Radio Electronics magazine, October 1984.
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...