The ST-LEQ1 has two line-level audio inputs and a single line-level audio output. The audio signal to be equalized connects to the EQ INPUT. If it is desired to mix an unprocessed source with the output signal, this second source is connected to the DIRECT IN input. Loudness equalization is applied to the EQ INPUT signal as the CONTROL voltage is varied.

The ST-LEQ1 may be operated together with any equipment which provides a 0 to 10 Vdc control. It is specifically designed to operate with other RDL equipment using 0 to 10 Vdc for level control. Because the ST-LEQ1 works with any RDL VCA module, all RDL remote level controls are suited for use with ST-LEQ1 Loudness Equalization. The line-level audio source is first fed through the RDL VCA product, then through the ST-LEQ1. The audio output from the ST-LEQ1 feeds the system amplifier or other equipment. The CONTROL terminals to the ST-LEQ1 are wired in parallel with the 0 to 10 Vdc terminals on the RDL VCA. The remote volume control associated with the VCA/ST-LEQ1 combination is adjusted to the normal low listening level, then the installer sets the desired loudness equalization on the multi-turn trimming potentiometer on the ST-LEQ1. As the listening level is increased by the remote control, the loudness equalization is progressively decreased until the audio is flat at normal higher levels.