Cross Wiring

One of the simple ways to look at it is the wiring on one side matches the field cabling... IE 36 pair cables wired from Pair 1 to Pair 36 in order and the next cable in order of pairs for all cables from field landiing all wires even spare conductors. The other side of the cabinet would be wired in order of the Control equipment IO. This is wired from card 1 point 1 to the last point on the card followed by the next card. Now the marshalling is where the cross wiring matches the input/output from the IO card to the cable/pair combination carrying the device signals from the field junction box or device.

I have also seen where the panel was large enough to allow the field wiring where the Control system Field Termination Assemblies FTA's were placed on one side of the panel and cables landed on the other side. this also keeps cables that have spare wiring to be laid on the floor of the panel... after a few years (10-20) the cables do not uncoil from the initial position...

This did a few things like making the wiring from the control system to a wiring point outside of the panel rather straight forward. From the field it allowed the cables to be easliy found when following in to the control room... the marshalled or Crossed wires were another problem... Usually in the first weeks after installation they are neat ...but given a little time an a few 2 in the morning call outs by the technicians the order is a little messy...

What I have seen lately is the use of barriers at the control system Marshalled IO location and a place to land the field cabling on the other side of the cabinet... some design considerations have to be established at the on set of the design such as the amount of IO and the cable types to be selected ie Cable Pair combinations such as 36 or 24 or 12 Pair cable types that allow for presizing the amount of area needed for marshalling...

Hope this helps...

RAL412