With the A-138j Inverting/Interrupting Mixer, Doepfer packs a mixer with four invertible inputs and quadattenuator in a compact module. Each of the four inputs can be used as attenuator respectively inverter; for this purpose each channel has its own output. The toggle switches allow to switch the respective channel on and off or to invert the input signal. If you plug a cable into one of the single outputs, it will be removed from the double mix output. The channels 1+2 have an additional B output, if a cable is patched here, the signal of the channel remains nevertheless at the mix output.