Black Box EYN257H-MF-50 50 ft IBM AT Null Modem Cable

Overview

The Black Box EYN257H-MF-50 is a 50-foot null modem cable designed for IBM AT-compatible serial device interconnects. Null modem cables eliminate the need for an intervening modem by cross-wiring the transmit and receive signal lines — making this a practical choice anywhere two serial DTE devices must communicate directly: legacy access control panels, serial-port DVRs, industrial controllers, or RS-232-based security equipment that predates IP-based communication. At 50 feet, the EYN257H-MF-50 provides enough reach to span equipment racks to nearby workstations or controllers without a signal repeater in straightforward installations.

Black Box has supplied structured cabling and connectivity components to enterprise and industrial environments for decades. The EYN257H-MF-50 (sometimes searched as EYN257H MF 50) ships in black, keeping cable runs visually clean in rack and panel environments.

Key Features

• Null Modem Wiring: Cross-connects TX/RX lines so two serial devices communicate directly — no external modem or converter required, which reduces points of failure in serial-dependent security and automation systems.
• 50-Foot Length: Spans the distance between equipment racks and workstations in most server room and control room layouts without requiring a signal extender, keeping your serial link simple and passive.
• IBM AT Compatibility: Designed for IBM AT-style serial pinouts common on legacy security panels, industrial PLCs, serial-port DVRs, and access control hardware still in active deployment.
• Black Jacket: Clean appearance in rack environments; easy to distinguish from patch cables in mixed-use wiring closets and security equipment rooms.

Integration & Compatibility

The EYN257H-MF-50 is intended for RS-232 serial connections on IBM AT-compatible equipment. Verify the DB9 or DB25 connector gender and pinout requirements of your specific devices before ordering — null modem cables vary in connector gender configuration, and the mating connectors on your serial port panel or device must match. For longer runs or electrically noisy environments, consider whether your application requires an RS-232 to RS-422/485 converter rather than a passive cable extension.

Frequently Asked Questions

Q: What is the EYN257H-MF-50 used for?

A: The EYN257H-MF-50 is a 50-foot null modem cable for direct serial (RS-232) communication between two IBM AT-compatible DTE devices, bypassing the need for a modem. Common uses include connecting legacy security panels, serial DVRs, or industrial controllers to local workstations.

Q: What connector types does the EYN257H-MF-50 use?

A: The cable is designed for IBM AT-compatible serial connections. Verify the specific connector genders (DB9 or DB25, male or female at each end) against your device requirements before ordering — connector configuration details are not confirmed in available evidence.

Q: Is the EYN257H-MF-50 suitable for long cable runs in electrically noisy environments?

A: RS-232 passive cables like the EYN257H-MF-50 are generally rated for short to moderate distances. For electrically noisy industrial environments or runs beyond standard RS-232 limits, an RS-422/485 converter is typically the more reliable approach.

Q: What color is the EYN257H-MF-50?

A: The EYN257H-MF-50 ships in black.

Eden Phillips

The EYN257H-MF-50 is a straightforward 50-foot null modem cable — exactly the kind of component that gets overlooked in a project BOM until someone is standing in a server room with two serial devices that won't talk to each other. Black Box built this for IBM AT-compatible serial pinouts, which still appear in legacy access control panels, older serial-port DVRs, and industrial automation equipment that hasn't been replaced on an IP migration cycle.

Technical Highlights:

• Null Modem Wiring: TX and RX lines are crossed at the cable level, enabling direct DTE-to-DTE serial communication — no modem, no converter, no additional power required in the link.
• 50-Foot Passive Reach: At 50 ft, the EYN257H-MF-50 covers most in-room equipment-to-workstation spans without amplification, keeping the serial link passive and low-maintenance.
• IBM AT Pinout Targeting: Designed specifically for AT-class serial devices, which differ in pinout assumptions from generic RS-232 null modems — using the correct cable avoids handshaking and flow-control mismatches that are notoriously hard to diagnose.

Deployment Considerations:

• Confirm connector gender at both ends before deploying — the MF designation indicates male-to-female, but verify against your specific panel or controller port before the cable ships to site.
• RS-232 at 50 feet is near the practical limit for reliable communication at higher baud rates in environments with any ambient electrical noise; if you are running in an industrial or rack environment with switching power supplies nearby, test at your target baud rate before commissioning.

This cable is best suited for legacy security system integrations — specifically connecting older serial-port DVRs, access panels, or IBM-compatible industrial controllers to a local management workstation where a 50-foot passive run is sufficient and IP-based alternatives are not available or not justified by the scope of the project.