Matrix Wire Trunk
A member of the DigiWin - Syscon system.
The older Digitech door alarm muxes used a wiring scheme that allowed 9 wires to read the status of 20 doors. By using diodes in the door contacts, the same wires could be used by multiple doors. The diagram below shows the electrical representation of this method.
Five of the wires are used to "Send" data, and 4 wires are used to "Return". The diode negative end is towards the return wire so that the signal always flows in one direction only.
The diode is built into the switch, so these switches can only be used by the matrix style multiplexers or the Unimux replacement with matrix daughterboards.
Note that this system used a 10 conductor cable, with 1 wire as a spare. Four cables were used per multiplexer (Trunks A, B C and D) so that a total of 80 doors per multiplexer could be achieved.