Simplex 650-759 — RUI+ CPU motherboard for the 4100U.
The master motherboard is the backplane the CPU and its option cards plug into in the master controller bay. It carries the RUI (Remote Unit Interface) circuitry that the panel uses to talk to remote annunciators and other RUI devices, so a failure here takes out both processing and remote communication at once.
- RUI+ CPU / master motherboard
- For Simplex 4100U fire alarm control panels
- Commonly supplied with harness 734-008 as kit 742-516K
Confirm the panel and bay revision before ordering. Simplex master motherboards are not interchangeable across platforms — the 4100ES uses a different RUI+ CPU master motherboard, and earlier 4100U panels used an earlier board. Handle by the edges with an anti-static strap.
