HoneywellDCOM-232/485Serial Communication Interface FTA – One RS-232 and Two RS-485 / RS-422 Ports, 5 V DC 500 mA

Product Description

What this part is

A Honeywell DCOM-232/485 communication interface — a serial-communication field termination assembly (FTA). Its job is to give a Honeywell safety and control system physical serial ports: one RS-232 port and two RS-485 / RS-422 ports, brought out to field terminals so third-party devices, gateways, printers, panel PCs and serial-linked instruments can be connected. It runs from a low-voltage 5 V DC, 500 mA supply as marked on the assembly.

Correcting the source data

Earlier copy described this as a general communication module for PLC processors and HMIs. It is more specific than that, and the difference matters when you are ordering: this is a DCOM field termination assembly for the Honeywell Safety Manager / FSC (Fail Safe Control) family, supplied under the catalogue numbers FC-DCOM-232/485 and FS-DCOM-232/485. It is not a generic RS-232-to-RS-485 converter you can drop onto a DIN rail in front of any PLC, and it is not an Experion or a TDC-3000 I/O module. If you are not working on a Safety Manager or FSC system, this is almost certainly not the part you want.

Decoding the part numbers

DCOM — Honeywell’s designation for the digital/serial communication field termination assembly.232/485 — the media it presents: RS-232 plus RS-485 (RS-485 hardware also serving RS-422 four-wire connection).FC- and FS- prefixes — the Fail-safe Control system product-line prefixes Honeywell uses for Safety Manager and FSC hardware. FC-DCOM-232/485 and FS-DCOM-232/485 both appear in spares lists for this assembly; either number will find it.

Published data

Function: serial communication interface field termination assemblyPorts: 1 x RS-232 output port, 2 x RS-485 output ports (RS-485/RS-422 capable)Supply: 5 V DC, 500 mA, as marked on the assemblyPlatform: Honeywell Safety Manager and FSC (Fail Safe Control) systemsForm: board-level field termination assembly for cabinet mountingManufacturer status: legacy Honeywell safety-system hardware; sourced through surplus, exchange and system spares rather than general distribution

What this means in practice

Serial links are where a safety system meets the rest of the plant — a DCS gateway, a Modbus master, an operator station, a historian, a third-party burner-management panel. That link is often the least redundant thing in an otherwise triple-checked architecture, and when the FTA fails the safety logic keeps running but the plant loses its window into it. Because Safety Manager and FSC installations are life-safety systems in refineries, gas plants, boilers and turbine halls, they are also the installations least likely to be casually modernised — so shelf spares for the serial termination hardware have real operational value.

Verify the assembly number and revision against your installed hardware before ordering. Honeywell’s FTA range is large, the assemblies look broadly similar, and the safety-system prefixes (FC- versus FS-) and revisions are tracked in the system documentation for a reason. Any change to safety-system hardware should go through your site’s management-of-change process, be entered in the system’s configuration record and be proof-tested afterwards.

Quantity and configuration

One assembly, new old stock, open box.

What is not included

Cabinet, subrack or mounting plate, backplane, 5 V DC power supply, system cables and prefabricated FTA cables, serial field cabling, connectors and connector kits, terminating resistors for the RS-485 segments, controller or safety module, system software or configuration tools, licences, and documentation. No configuration, address setting or safety-system database is supplied or implied.

Installation notes

Confirm the 5 V DC supply is present, regulated and adequately rated before connecting — 500 mA is the assembly’s own requirement, separate from anything the connected devices draw. Terminate each RS-485 segment at both physical ends with the correct impedance and observe A/B polarity consistently along the run; reversed pairs and missing terminators produce intermittent link failures that look like a failing board. Use screened cable and land the screens per the system’s earthing scheme rather than improvising. Observe ESD precautions when handling the board.

On a live safety system, treat any hardware change as safety-related work: follow the site’s management-of-change procedure, record the change in the system configuration, and proof-test the affected functions before returning the system to service.

Interchange guidance

FC-DCOM-232/485 and FS-DCOM-232/485 are the designations for this assembly. Other Honeywell FTAs are different assemblies, not equivalents — the FTA range covers analogue input, analogue output, digital input, digital output, thermocouple, RTD and other serial types, and none of them substitutes for a DCOM. Generic third-party RS-232/RS-485 converters are not substitutes: they do not present the system-side interface, the mounting or the diagnostic behaviour the Safety Manager / FSC hardware expects.