Operated directly from the power grid, this detector was found in an 80's RCA documentation. The sensor is an ionization chamber. The SCR triggers a warning siren.
This circuit can operate in a 100 dB range with signals of up to 100 MHz frequencies. Similar...
This audio level indication system for microphones was found in Radio Electronics from the 90s....
This circuit was found in a 90’s Electronic Design. The circuit uses components that are still...