The ES-4 is a Eurorack format module which converts a standard S/PDIF input to five channels of control voltage.
Two of the five channels are calibrated to provide over 5 octaves of 1V/octave pitch CV. The remaining three channels are general purpose outputs (for use as e.g. gates, envelopes, LFOs) and each have a nominal range of 0-10V or ±5V (user selectable).
Since S/PDIF is a stereo-only format, the encoding of the five channels on to two is handled by software provided as part of Expert Sleepers Silent Way.
The ES-4 will connect to any audio device using the S/PDIF standard. This includes the digital audio output provided as standard on all recent Macs.
The front panel is drilled for both Doepfer and Analogue Systems mounting holes (using a 'slot' rather than a single round hole). The power connector is a Doepfer standard 16 way IDC, with -12V furthest from the top of the board.