This is one of the first radios with an integrated circuit. The circuit is from a Radio Electronics from November 1969. The circuit is powered by a 9 V battery.
This circuit is from a Popular Electronics from April 1991. The magazine no longer exists, but the...
The purpose of this circuit is to keep the other phones on the same line muted when one is used....
This highly-sensitive circuit causes a relay to be closed when the other is open or still...