Control Inputs; the top row of connectors.
There are 12 control inputs, also known as ‘General Purpose Inputs’ or ‘GPI’.
The control inputs are used to connect contact closures (for control of binary parameters, such as mutes), resistor ladders (for control of multistate parameters, such as source selectors) or potentiometers (for control of continuous parameters, such as volume faders).
There are two common (ground) connections labeled ‘C’ on the left most portion of the bottom row, and two software-assignable reference voltage outputs ‘R’ on the right most portion of the bottow row. The control ports have two modes of operation: 2-wire and 3-wire.
Control Inputs; the top row of connectors.