The integrated circuit used in this 2002 project is not very common. It is powered directly by the telephone line, requiring no power supply.
This circuit is from a 1991 publication. The integrated circuit used is an integrated radio from...
This receiver for listening to the TR-23 phone was manufactured in Japan in the 1960s. The circuit is...
Found on a 1965 Radio Electronics, this circuit fires a signal xenon lamp applied to the SCR from...