This two-door doorbell was found in a 1990s US publication. The circuit is still current as transistors may be commonly used. The circuit produces different tones depending on the activated door. Power must come from a power supply.
This two-door doorbell was found in a 1990s US publication. The circuit is still current as transistors may be commonly used. The circuit produces different tones depending on the activated door. Power must come from a power supply.
