VOICE ACTIVE SWITCH (DELAY OFF)
Just as we can demonstrate light activated switches, the FK408 uses sound as its triggering input. A microphone detects the sound which is amplified to drive a relay. A 0-60 second, adjustable timer can be set to hold the output relay on for a preset time after the sound has stopped. As a class project, students may experiment with various filter designs inserted after the microphone to make the FK408 only operate at specified frequencies.