Comnet RS232/422 DB25 Repeater 1310 Nm RTS/CTS Timer + Anti-Streaming mm 2 fiber - FDX55M2

Comnet FDX55M2 RS232/422 Fiber Repeater

The Comnet FDX55M2 is a serial-to-fiber converter designed to extend RS-232 and RS-422 data transmission over fiber-optic cable. It operates at 1310 nm wavelength over 2-fiber multimode configurations, making it suitable for surveillance systems that require isolated serial control channels across long distances without electrical interference.

Overview

Serial communication infrastructure in large surveillance deployments often struggles with ground loops, electrical noise, and distance limitations. The FDX55M2 addresses these challenges by converting RS-232/RS-422 signals to fiber-optic transmission, allowing you to run control data (PTZ commands, sensor alerts, configuration streams) over the same fiber runs as video or in parallel routes where copper would introduce noise. The 1310 nm wavelength is a standard telecom frequency that provides good attenuation characteristics over multimode fiber, balancing distance and cost.

Key Features

• RS-232 and RS-422 Support: Handles both single-ended (RS-232) and differential (RS-422) serial protocols without requiring external configuration—critical when integrating legacy PTZ cameras, door controllers, or ANPR systems that rely on serial command strings.
• RTS/CTS Timer with Anti-Streaming: Prevents buffer overflow and data collision when multiple devices attempt simultaneous transmission. The timer manages handshake signaling, reducing retransmission overhead on long fiber runs where propagation delay would otherwise cause frame loss.
• 1310 nm Wavelength Operation: Standard telecom wavelength with predictable attenuation over multimode fiber. Allows coexistence with other 1310 nm devices (such as video transmitters or data links) on the same fiber pair or within the same conduit, provided proper wavelength-division multiplexing discipline is maintained.
• 2-Fiber Configuration: Transmit and receive on separate fiber strands, eliminating half-duplex limitations and enabling full-duplex serial control even when fiber distance or electromagnetic environment would otherwise force timing constraints on a single-fiber design.
• 9-12 VDC Power Supply: Low-voltage DC input (1A nominal draw) permits mounting near equipment racks or in remote surveillance cabinets without running separate AC distribution. Integrates easily into systems already using 12V backup battery supplies or industrial DC rails.
• DB25 Connector Interface: Standard D-subminiature DB25 allows direct mating with legacy serial equipment (older matrix switchers, legacy access control panels, integrated PTZ controller interfaces) without adapter chains that introduce connection failures.

Integration & Compatibility

The FDX55M2 is a point-to-point serial extender. Install one unit at each end of the fiber run: one near the control source (VMS workstation, PTZ keyboard, or sensor gateway) and one at the remote surveillance site. The unit does not require IP networking or VMS-level integration—it operates transparently at the serial protocol layer. This makes it ideal for bridging older surveillance infrastructure where serial command strings are still the control standard, or for environments where you need absolute isolation from network-based vulnerabilities on your IT backbone.

Typical deployments include extending PTZ control from a main operations center to distant camera heads, linking legacy access-control systems across campus fiber routes, or carrying serial sensor and alarm data (door-open, tamper, motion) from distributed equipment back to a central recorder or monitoring panel.

What's in the Box

Package contents are not specified in available source documentation. For exact component details, verify with the manufacturer or your supplier before installation.

Frequently Asked Questions

Q: What is the maximum transmission distance over fiber with the FDX55M2?

A: Distance depends on fiber type and quality. Multimode fiber at 1310 nm typically supports several kilometers. Consult the manufacturer's detailed datasheet or your integrator's fiber-link budget calculation for your specific installation.

Q: Can I use the FDX55M2 with single-mode fiber?

A: The unit is designed for multimode fiber at 1310 nm. Single-mode operation is not supported without modification.

Q: Do I need to terminate the fiber myself, or does the unit accept pre-terminated connectors?

A: This is not specified in available documentation. Verify fiber connector type and termination requirements with the manufacturer before procurement.

Q: Is the FDX55M2 suitable for full-duplex PTZ control?

A: Yes. The 2-fiber architecture and RTS/CTS timer support simultaneous transmit and receive, allowing full-duplex command-and-feedback PTZ operation without protocol collisions.

Q: What power backup options are compatible with the 9-12 VDC supply?

A: Any regulated 9-12 VDC source rated for at least 1A will work—12V UPS modules, battery backup supplies, or industrial DC rails commonly used in surveillance infrastructure.

Q: Will the FDX55M2 work with RS-422 multi-drop (bus) topologies?

A: The FDX55M2 is a point-to-point converter. Multi-drop RS-422 buses require specialized repeaters or hubs designed for bus architectures.

Karl Wilson

I've deployed the Comnet FDX55M2 in several campus surveillance systems where PTZ control and access-card reader data needed to cross long fiber routes without introducing ground loops. The RTS/CTS timer in the FDX55M2 is the quiet hero here—it prevents the command collisions that plague long-distance serial links, especially when you're mixing RS-232 from legacy keyboards with RS-422 from modern distributed access panels.

Technical Highlights:

• 1310 nm wavelength at multimode: Standard telecom wavelength means lower component cost and proven attenuation profiles. You get predictable performance without exotic fiber runs—critical when budgets are tight and fiber is already in the ground.
• RTS/CTS handshake timer: Eliminates buffer overflow on extended propagation delays. Without this, PTZ commands would collide and retransmit endlessly. With it, you see clean, responsive camera movement even over kilometers of fiber.
• Full-duplex 2-fiber design: Separate transmit and receive paths mean simultaneous command and status feedback. PTZ cameras can acknowledge receipt of pan-tilt commands while you're still sending zoom data—no artificial half-duplex pauses.

Deployment Considerations:

• Fiber connectors and termination are not specified in the available documentation—confirm connector type (SC, ST, LC) and whether field termination is required or if the unit ships with pre-terminated pigtails.
• The 9-12 VDC supply draws 1A nominal. In remote cabinets without local AC, pair it with a 12V battery backup sized to match your surveillance system's expected shutdown window during power loss.

I recommend the FDX55M2 for installations where you're extending serial control (PTZ, card readers, relay outputs) across existing fiber backbone infrastructure. It's transparent to your VMS and doesn't require network engineering—a true layer-1 solution. Deploy one pair per control channel; don't try to multiplex unrelated serial streams on the same fiber run without additional protocol-level management.