This circuit was found in a 90s American publication. The same configuration appears in several places on this site, obtained from different sources. The lamps can be replaced by LEDs.
June 2017 - The new touch screens with resistive sensors of the FK Series from NKK Switches can...
This circuit lets through the 300 Hz to 3kHz range that corresponds to the human voice. We found it...
This circuit, found on Motorola's Linear Interface ICs uses the MC1536 as a driver for a 36 W or...