An HD (high definition) box typically refers to the electronic component that receives a cable TV signal and sends it along to a connected television. Modern HD boxes are equipped with a variety of jacks, inclduing digital audio outputs for connecting cable service to a home theatre sound system. The signal from the HD box may carry up to eight channels of audio for a 7.1 surround sound system. A single digital cable connects the box directly to the audio input on the sound system receiver.
Shut off the power to the surround sound receiver and the HD box before connecting any cable.
Turn the plug on one end of the digital audio cable so the shape of the plug matches the outline of the digital audio output jack on the back of the HD Box. Push the plug straight in.
Connect the other plug on the cable to the digital input socket on the back of the surround sound receiver.