This circuit is for old telephones with analog lines. It was found in the May 1988 Radio Electronics magazine. The circuit is powered by the line signal voltaje.
This is a circuit published in the January 1962 Radio Electronics magazine. The circuit is for...
This diagram was found in the November 1972 issue of Radio Electronics magazine in an article...
This circuit with the CK722 was found in a Raytheon publication from the 60's. The relay is of the...