The multi-mode STL-1 functions as two separate direct boxes in stereo mode. In the mono mode, two high impedance, unbalanced input signals can be combined into one low impedance, isolated balanced output mono signal to conserve channels in a snake. Also in the mono mode, two high impedance unbalanced signals can be combined into one low impedance balanced signal, isolated and split into two separate mono output signals. Comes with two shunts on the input to eliminate feedback.