DTMF-4HC is an inexpensive, self contained, DTMF (dual tone multiple frequency) decoder board which permits users to control remotely, via radio or other audio producing source, the on or off state of four high current devices. For larger applications several DTMF-4HC boards can be attached to the same control audio source to control dozens of devices. DTMF-4HC supports four modes of operation. These mode settings control how the DTMF-4HC behaves.