We found this circuit in the February 1983 issue of Radio Electronics magazine. The 4-digit circuit is based on dedicated integrated circuits of the time. The power supply is not shown.
August 2017 - Mouser Electronics is announcing the availability of TDK ICS-52000 microphones with...
This circuit, which can be used as a shield or in other applications, can be found elsewhere on...
This crystal or galena radio was found in documentation from the 1990s. The earpiece must be a...