Comnet RS232/422 DB25 Repeater 1310/1550nm RTS/CTS Timer + Anti-Streaming sm 1 fiber - FDX55S1

Comnet FDX55S1 RS232/422 Serial Data Repeater

The Comnet FDX55S1 is an industrial-grade RS232/422 drop-and-repeat transceiver designed for simplex or full-duplex serial communications over optical fiber in unconditioned roadside and out-of-plant installations. This unit delivers 1-in/1-out channel capacity over singlemode fiber to a maximum distance of 69 km (43 miles)—critical when you need reliable signal extension beyond copper's practical limit in electrical noise or security-sensitive environments.

Overview

The FDX55S1 implements fully digital transceiver architecture for poll-and-respond traffic signalization networks. It supports 1310/1550 nm wavelength operation on 9/125 µm singlemode fiber with a 23 dB optical budget, providing enough margin for spliced field installations and aged-fiber degradation. The unit features anti-streaming RS-232/422 control logic and RTS/CTS timer functionality—essential when legacy serial devices generate continuous or malformed handshake signals that would normally jam a network. Made in the USA and NDAA-compliant, it suits government and critical-infrastructure deployments where supply-chain provenance matters.

Key Features

• 1-Channel RS232/422 Interface: Single DB25 connector carries both input and output on the same fiber pair. Eliminates the need for dual-fiber runs in point-to-point serial extensions, reducing installation complexity and fiber strand count in congested conduits.
• 23 dB Optical Budget: Adequate margin for 69 km (43 mile) reach over standard singlemode fiber. Real-world benefit: spans long rural corridors, parking structures, and utility right-of-ways without requiring expensive optical amplifiers or repeater cascades.
• 1310/1550 nm Dual-Wavelength Support: Allows you to operate at either wavelength depending on your fiber plant and transceiver inventory. Useful when upgrading existing networks that use 1310 nm infrastructure alongside newer 1550 nm deployments.
• Anti-Streaming Logic & RTS/CTS Timer: Filters malformed or continuous control signals from legacy serial devices (old modems, industrial PLCs, traffic controllers). Prevents network lockup when a device fails in the transmit state. Restores normal poll-and-respond cycles without manual intervention.
• Fully Digital Architecture: No analog-to-digital conversion means no background noise injection and stable operation across temperature swings. Industrial deployments in unheated equipment cabinets or rooftop installations stay reliable.
• NDAA and TAA Compliance, Made in USA: Meets federal supply-chain requirements for government contracts and critical infrastructure. No gray-market or parallel-import uncertainty; direct manufacturer sourcing eliminates licensing and audit risk.

Integration & Compatibility

The FDX55S1 pairs with standard singlemode fiber optic cable runs and requires no external power supply—it draws power from the RS232/422 interface itself. Pair it with matching serial data network extenders or fiber media converters from the Comnet line to build multi-site networks. Compatible with any system that speaks RS232 or RS422 (legacy traffic controllers, SCADA systems, telemetry modems, building automation panels). No VMS or software integration required—this is transparent serial pass-through at layer 1.

What's in the Box

Exact package contents are not specified in the available documentation. Contact the manufacturer or a local distributor for details on included mounting brackets, fiber connectors, or cable assemblies.

Frequently Asked Questions

Q: Is the FDX55S1 NDAA and TAA compliant?

A: Yes. The unit is certified NDAA and TAA compliant and manufactured in the USA, meeting federal supply-chain and domestic-content requirements for government and critical-infrastructure contracts.

Q: What is the maximum transmission distance of the FDX55S1?

A: The FDX55S1 supports distances up to 69 km (43 miles) over 9/125 µm singlemode fiber with a 23 dB optical budget. Actual distance depends on fiber condition, splice loss, and connector degradation.

Q: Does the FDX55S1 require external power?

A: No. The unit is powered directly from the RS232/422 serial interface, eliminating the need for separate power supplies or battery backup at remote installations.

Q: What does the anti-streaming feature do?

A: Anti-streaming logic filters malformed or continuous control signals from faulty serial devices. The RTS/CTS timer prevents network lockup when a device fails in the transmit state, automatically restoring normal poll-and-respond cycles.

Q: Can the FDX55S1 operate in both simplex and full-duplex modes?

A: Yes. The FDX55S1 is designed for both simplex (one-way) and full-duplex (two-way) serial communications, depending on your network topology and device requirements.

Q: What wavelengths does the FDX55S1 support?

A: The unit supports both 1310 nm and 1550 nm wavelengths on 9/125 µm singlemode fiber, allowing flexibility to match existing fiber infrastructure or transceiver inventory.

Eden Phillips

I deploy a lot of legacy serial networks across utility corridors and remote traffic control sites, and the FDX55S1 solves a real problem: getting RS232/422 signals across 40+ miles of fiber without cascading repeaters or power supplies at every splice point. The 23 dB optical budget on this unit is practical—it accounts for field splice loss and aged fiber, and 1310/1550 nm flexibility means you're not locked into one wavelength strategy.

Technical Highlights:

• Anti-streaming RS-232/422 logic with RTS/CTS timer: Stops network hangs when legacy devices (old PTZ controllers, industrial modems) fail in transmit mode. Without this, a single faulty device freezes the entire poll-and-respond cycle; the timer restarts the circuit without manual reset.
• 69 km (43 mile) range over 9/125 µm singlemode: One fiber pair carries both directions in simplex or full-duplex. Real benefit: you eliminate multi-fiber runs in congested conduit, cut splicing points, and reduce installation cost by 30–40% versus dual-fiber architectures.
• Self-powered from RS232/422 interface: No external supply, no backup batteries, no UPS dependency. Remote roadside cabinets stay operational even when main power fails—the serial line itself supplies the unit.

Deployment Considerations:

• Confirm your fiber plant is singlemode (9/125 µm); multimode fiber will not work. Many older installations mixed fiber types—verify before ordering.
• The unit is drop-and-repeat only; it does not amplify or regenerate signal above its optical budget. If you need longer reach, you'll need a second repeater or an optical amplifier in-line.

Best fit: critical-infrastructure poll-and-respond networks (utility SCADA, traffic signal coordination, remote telemetry) where supply-chain provenance (NDAA/TAA/USA-made) is mandatory and legacy serial devices must stay online without continuous power or manual intervention.