Simplex 734-075 — Harness, Power/Comm Box to Box, Simplex assembly 4100-0636, a service part for 4100U and 4100ES fire alarm control panels.
A 4100U or 4100ES grown past one enclosure must carry its 24 V power and its internal communication bus across to the next back box, and Simplex supplies that link as a made-up harness rather than loose wire so the connectors and length are right. The parts lists draw a hard line between bay-to-bay harnesses, which link card bays inside one enclosure, and box-to-box harnesses like this one.
- Simplex description, verbatim: Harness, Power/Comm Box to Box (4100-0636)
- Listed under Harness Assemblies in 4100ES Service Parts List 579-1006 Rev. A
- Listed under Harness Assemblies in 4100U Service Parts List 579-330 Rev. W
- Carries power and communication between enclosures, not between bays
The neighbouring codes are a real trap: 734-076 is Audio Box to Box (4100-0637), 734-087 is Legacy to PDI Pwr/Comm Box to Box, 734-084 is the Bay to Bay version, and 734-095 is the Additional 24V harness (4100-0638).
