Allen & Heath DSP Rack Module for iDR0:

Besides the channel inputs, insert points, and direct outputs already mentioned, there is a row of six jack sockets for the aux send outputs. When these are used to send signals out to effects, the returning signal can be plugged into either one of the two pairs of jack sockets labelled ST1 and ST2, although the unbalanced ST2 is partly intended as an audio input for a device playing pre-recorded interval music during live shows. These inputs are situated next to a pair of impedance-balanced outputs marked AB, which offer an alternative version of the stereo mix and are intended for sending a signal to an external stereo recorder. Just below the AB outs is a blanking panel where the Sys-Link II option can be added