24 Channel Duplex Contact Closure Transceiver

FDC24NL Series

Example of 24 Channel Duplex Contact Closure Transceiver

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-40 º to +75 ºC




Made in the USA



The ComNet FDC24NL Series contact closure transceiver units provide transmission of up to twenty four independent duplex dry switch or relay contact closures using a single SFP* optical port or any four-wire RS-422 copper circuit. The FDC24NL Series supports an integrated field expandable RS-422 data bus allowing up to 12 uniquely addressed units to be connected to the bus providing up to 288 unique duplex contact closures over a single SFP optical port or RS-422 copper circuit. The contact closure information is sent in packets that are ordered and encoded, ensuring extremely robust transmission. Packets that are garbled, packets out of sequence, and transmission bit errors will not cause random changes of state on the contact relays. One relay can be optionally re-purposed as a summary fault alarm contact and is triggered in the event that the unit loses fiber or RS-422 bus communications. The FDC24NL series is offered with non-latching solid state relays. Each module incorporates link and individual status indicating LEDs for monitoring confirmation of contact closure input and output of each of the twenty four channels. Packaged in the exclusive ComNet ComFit housing, these units may be either wall or rack-mounted, or may be DIN-rail mounted by the addition of ComNet model DINBKT1 or DINBKT4 adaptor plate.

Features for FDC24NL Series

  • Designed to meet full compliance with the environmental requirements (ambient operating temperature, mechanical shock, vibration, humidity with condensation, high-line/low-line voltage conditions, and transient voltage protection) of NEMA TS-1/TS-2 and the Caltrans Specification for Traffic Signal Control Equipment.
  • Supports multiple units with the same address providing one-to-many or many-to-one contact closure type scenarios.
  • Transmits up to twenty-four duplex independent dry switch or relay contacts over one SFP fiber port, or via a 4-wire RS-422 copper circuit.
  • Unique cascadable data bus design allows for easy system expansion of up to 12 uniquely addressed units (288 unique duplex contacts) over a single SFP port or RS-422 copper circuit.
  • ComFit standard form factor is interchangeable between stand-alone or rack mount use.
  • Standard ComFit models are hot-swappable.


  • Alarm Event Triggering
  • Fire Alarm & Intrusion Detection Systems
  • Lane/Gate Control
  • PIR Signal Transmission
  • Building Automation and Environmental Control Systems

FDC24NL Series Application Diagram(s) (2)

Application Diagram(s) for FDC24NL SeriesApplication Diagram(s) for FDC24NL Series

FDC24NL Series Ordering Information

Part NumberDescription
FDC24NL24-Channel Duplex Contact Closure Transceiver (Non-Latching Relays), RS-422 Interface. Lifetime Warranty.
FDC24NLSFP24-Channel Duplex Contact Closure Transceiver (Non-Latching Relays), SFP Interface. Lifetime Warranty.