The ES12 contains 3x voltage controlled routers that can route one input to either of two outputs, or either of two inputs to one output according to the voltage level at the 'control' input.

The CONTROL switch point is, nominally, around 2.5V. When the CONTROL is low the signal path is A1 <--> B and when CONTROL is high the signal path is A2 <--> B

The switches are true bidirectional switches. You can feed signals through them in either direction. Note that due to the limits of CMOS, it can switch signals that are up to about +/-9 volts.

Build Guide