Data Over Distances
One of the things that builders need to contend with is the potential mangling of data when it has to travel long distances; the console to chamber data cable itself can be a couple hundred feet. Anything under 6 feet we generally don't have to worry about, over 6 feet in the Legacy System, we use an RS-422 protocol. Maestro uses Ethernet.
This is a standard set by the Electronic Industries Alliance. It uses differential signalling, which means 2 complementary signals are sent out, each on their own wire, for the data. The receiving chip then looks at the difference between the 2 signals rather than looking at the difference between the signal and ground. Differential signalling can transmit data rates as high as 10Mbit/s over 1500m. What this means for you as the builder is, for every piece of information you need to send, for example Clock, you will used 2 wires twisted together.
Sometimes we specify using a shielded cable, sometimes a shield is recommended. The drain wire on the cable is always connected to ground on the board 'farthest away'. So, for example, the shielded cable which goes from the Console to the Chamber has the shield connected to ground in the chamber.
Console to Chamber
The cable between console and chamber can easily run 200ft in a larger church, so we specify a 6-pair twisted shielded data cable. The pairs are for Strobe, Data, Clock, MIDI Expander, Temperature Sensor, and a Relay signal. The Strobe, Data, Clock, and MIDI use the RS-422 standard, so they will each have a paired signal. The temperature and relay are simple voltage levels, they don't need a paired signal, so the second wired in their pairs is ground. On a discrete system the shield is connected to ground in the chamber, possibly at the conduit, in a grey box system there are two extra pins (13 and 14) the shield may be connected here.
Some builders have been known to use CAT-5 cable, when they do not need all 6 pairs. We do not recommend this. First CAT-5 is not shielded, second if somebody wants to make a change in the future, and they now need all 6 pairs, they are going to have to run a new cable.
Pipe Driver Boards
The length of cable between the Pipe Control Computer and a Pipe Driver Board may not exceed 6 feet. Even if the two boards are right beside each other, if the cable loops around or goes around corners these loops must be accounted for, it's not the distance between the board but the length of the cable.
Sometimes a Pipe Driver Board needs to be mounted at a greater distance from the Pipe Control Computer. This is most commonly found with something like a Festival Trumpet rank, or a small Antiphonal division. In such cases we can provide an RS-422 connection between these board. We can build the Pipe Control Computer (PCC) with 4 differential outputs, if you tell us in advance. If you need more than 4 drivers at a greater distance, we can provide Line Driver Boards, which converts the standard serial data into RS-422, but the better course in most situations is to use another Pipe Control Computer.
Chamber Grey Box
Cables being more than 6 feet long is generally not an issue in a grey box system, as the driver board are mounted inside the grey box, and we do the wiring. Occasionally just like in a discrete system 1 or 2 of the driver boards may need to be mounted at a greater distance, and we do provide RS-422 connections on the side panel.
Chimes Driver Board
The Chimes Driver Board (CDB-5A) is susceptible to interference so must use one of the RS-422 connections on the PCC, keep this in mind if you are planning on using the four RS-422 for pipes.