DSP5D Digital Mixing System
The DSP5D provides essentially all the functionality of a PM5D-RH - minus the control surface - in a rack-mountable unit that can be seamlessly controlled from a PM5D (RH) console. In terms of I/O capacity and processing capability the DSP5D offers:

Up to two DSP5D units can be used with a single PM5D console. A PM5D plus one DSP5D gives you 4 input fader layers, with a total of 96 mono and 16 stereo input channels, while adding two DSP5D units to a PM5D provides 6 layers with 144 mono and 24 stereo input channels to comfortably handle large-scale applications.
And of course your processing power is doubled or tripled, respectively. Like the PM5D itself, all analog inputs and outputs are directly accessible via standard XLR type connectors.
After a few simple connections the DSP5D becomes an integral part of the PM5D console, and can be controlled from the PM5D control surface in the same way as the internal functions.
So although you have significantly upgraded the system, you can simply plug in your sources and output devices and use it right away without having to work through another learning curve.
DCU5D Digital Cabling Unit
You can directly connect the DSP5D to a PM5D via standard cascade cables if they are to be used in relatively close proximity. But if you want to use the DSP5D as a powerful stage box the DCU5D Digital Cabling Unit lets you locate the DSP5D as far as 120 meters* from the PM5D console, connected only by one Cat-5 Ethernet cable (appropriate high-performance cable).
The DCU5D converts the PM5D cascade signals (68-pin D-sub connector) to and from Cat-5 audio, dramatically reducing cabling requirements while maintaining solid audio and control reliability over extended distances.
Distance may vary depending on cable performance.
System Examples
1. Expanded PM5D

This is the simplest PM5D + DSP5D system, with a single DSP5D connected directly to a PM5D console via a pair of cascade cables. But although it is simple to set up, this system expands your microphone input capacity from 48 inputs to 96 inputs, and matrix buses from 8 to 16.
2. Dual Remote DSP5D Units via a DCU5D

In this system a DCU5D Digital Cabling unit is used to allow two DSP5D units to be located on stage, a considerable distance from the front-of-house PM5D console. The only physical connections between the front-of-house location and on-stage DSP5D units are one Cat-5 Ethernet cable. With this setup you have a total of 144 channels, and 24 matrix buses. PM5D provides all the necessary control for the two DSP5D units, and remember that one computer running Studio Manager for all three devices will add even more versatility.