Preliminary architecture BOM for schematic capture and sourcing review. Quantities are per receiver. MPNs must be rechecked against current datasheets, distributor stock, lifecycle, module certification, and Flux footprint quality before purchase or PCB release.
Recommended Core ComponentsPower Input and ProtectionBuck Regulator Support ComponentsLogic, Reset and DecouplingRelay Drivers and IndicatorsField and RF ConnectorsTiming Components for External WatchdogMechanical and Assembly ItemsPreliminary Cost and Sourcing Notes
Relays, pluggable terminals, radio module, enclosure, and assembly labor are expected to dominate unit cost.
The detailed specification and BOM are now drafted. I found and corrected a critical inconsistency in the earlier notes: communications relays must be energized when healthy and use COM–NC so loss of receiver power produces an alarm.
Created the detailed Project Specification and Preliminary BOM, including architecture, fail-safe COM–NC communications alarms, power budget, interfaces, PCB/enclosure requirements, verification criteria, recommended MPNs, and alternatives. Remaining work is final datasheet/availability verification for the radio SKU, relays, power supply, antenna certification conditions, Siemens input module, and enclosure; further execution is paused because no ACUs are currently available.