Controls for the adjustment, most often, of treble and bass. Toslink - A a squarish connector for a fiber optic cable used for DVD optical audio output. Often the entire cable is referred to as a Toslink cable. It is also called an optical cable.
The control on a preamplifier, integrated amplifier, or receiver that boosts or cuts certain segments of the audible bandwidth. Bass and treble controls are the most common versions, but some units have midrange controls also. See also Equalizer