This circuit was found in the August 1993 Electronics Now magazine. It is for telephones used on common old-style analog lines.
We have here a very interesting project found in a 1982 publication. By the operation of the...
We found this circuit in an old American manual. The formulas allow the gain to be calculated as a...
This circuit is from the time when cars used contact breakers. This 80's version measures the dwell...