Tendzone TYCHO T 1212/CA - Manual (Page 27)

As is shown in the chart, pin of GPIO output channel 2 outputs low level when the level of audio matrix input channel 1
reaches -20dB.
c) Muted Channel Display
As is shown in the chart, pin of GPIO output channel 3 outputs low level when the audio matrix output channel 3 is muted.
d) Muted System Display
As is shown in the chart, pin of GPIO output channel 4 outputs low level when all the output channels of the audio matrix
are muted.