24V x TTL Interface (CB24898E)

The figure shows how to interface a 24 V signal with TTL logic using a 4N26 coupler. The circuit is from Radio Electronics from May 1985.

Dwell Meter (CB4961E)
This circuit is from the time when cars used contact breakers. This 80's version measures the dwell...
Tolerance Indicator For Capacitors (CB4650E)
The basic idea of this circuit is to indicate the tolerance of a capacitor by reference to a...
Multitester (CB3834E)
This simple multitester tests continuity, semiconductors, leaks, and other common component...