Discrete: In the console, the Console Control Computer and other console-related circuit boards are installed individually by the organ builder. Similarly, in the pipe-chamber, the Pipe Control Computer and all the associated pipe-chamber circuit boards are separately installed and wired by the builder.  The discrete approach is significantly more cost effective if lighted rocker tabs (LRT's) are used for stops, and/or optical keyswitch rails (with piston scanning) or CLASSIC CMK keyboards (also with piston scanning) are used.

Packaged: The Console Control Computer and all the circuit boards of the console system are installed in a grey, metal box, the Console Control Unit (CCU/LCCU), at the Classic Organ Works factory. All the console controls (keyboards, pistons, stop knobs, etc.) are wired by the builder to the pins on the exterior of the grey box. For the pipe-chamber, there is a similar grey box, the Pipe Control Unit (PCU/LPCU), containing the Pipe Control Computer or UIB and all the pipe-driving circuit boards.  The "Grey Box" approach is most cost effective if conventional "all-parallel" wiring techniques are used in the console.  Also, having chamber components packaged in grey boxes, reduces install time, and eliminates inter-board wiring.