Black Box EYN257H-FF-40 40-Foot IBM AT-AT Null Modem Cable

Overview

The Black Box EYN257H-FF-40 is a 40-foot null modem cable built for IBM AT-AT serial device connections. At 40 feet, it gives you enough reach to bridge a control console or terminal to a serial device across a rack room or equipment bay without a signal repeater — a practical length for server room or data center serial management runs where equipment is not co-located.

Null modem cables cross the transmit and receive lines internally, eliminating the need for a DCE device (modem) between two DTE endpoints. That means direct host-to-host or host-to-terminal serial communication without additional hardware — useful for out-of-band management consoles, legacy device configuration, or serial equipment commissioning where a live network connection is not available or appropriate.

Note: The EYN257H-FF-40 (sometimes searched as EYN257H FF 40) is designated non-cancelable, non-returnable. Confirm your serial pinout requirements and cable length before ordering — returns are not accepted on this SKU.

Key Features

• 40-Foot Run Length: Covers the span between separate equipment cabinets or a wall-mounted patch panel and a floor-standing rack without extension cables or additional hardware in the signal path.
• Null Modem Wiring: Crosses TX/RX internally so two DTE serial devices communicate directly — no standalone modem required. Standard configuration for terminal-to-host and console-to-server serial links.
• IBM AT-AT Compatibility: Pinout matched to IBM AT serial port standards, making it a direct fit for legacy IBM-compatible hardware, console servers, and serial terminal equipment using DB9 or compatible AT-spec connectors.
• Black Jacket: Low-visibility black finish suits equipment room and rack environments where cable management aesthetics matter.

Integration & Compatibility

Designed for IBM AT-AT serial port configurations. Verify connector gender (female-female based on product designation FF) and pinout against your specific equipment before deployment. Suitable for serial console management, legacy terminal emulation, and direct device-to-device serial links in environments where RS-232 null modem wiring is required.

Frequently Asked Questions

Q: What does the null modem wiring on the EYN257H-FF-40 mean for my installation?

A: Null modem cables cross the transmit and receive signal lines internally, allowing two DTE devices (such as a PC and a serial terminal or console server) to communicate directly without an intervening modem or DCE device.

Q: What connector type does the EYN257H-FF-40 use?

A: The FF designation indicates female-female connectors on both ends, matched to IBM AT-AT serial port standards. Verify your equipment's serial port gender before ordering.

Q: Can I return the EYN257H-FF-40 if it does not fit my application?

A: No. This SKU is designated non-cancelable, non-returnable. Confirm your connector type, pinout, and required cable length before placing your order.

Q: Is 40 feet long enough for cross-rack serial console runs?

A: For most single-room equipment bay or server room deployments, 40 feet is sufficient to bridge two adjacent or nearby racks. For longer runs, verify RS-232 signal integrity at your baud rate before deploying a longer cable without a signal booster.

Karl Wilson

The EYN257H-FF-40 is a straightforward 40-foot null modem cable — the kind of part that sits in a parts drawer until the day you need it for an out-of-band console session on a legacy serial device and nothing else on site will reach. The 40-foot length is the spec that matters most here: it covers the typical gap between a dedicated serial console server and a remote device in an adjacent rack or across a raised-floor equipment room without daisy-chaining shorter cables.

Technical Highlights:

• 40-Foot Length: Spans cross-rack and cross-bay serial runs without extension hardware — a practical choice when your console server and target device are not co-located in the same cabinet.
• Null Modem Wiring: TX/RX lines crossed internally for direct DTE-to-DTE communication — eliminates the modem hardware from the signal path on IBM AT-AT serial links.
• Female-Female (FF) Connector: Both ends terminate in female connectors, matching the male DB9 serial ports standard on IBM AT-compatible equipment without requiring a gender changer adapter.

Deployment Considerations:

• Confirm your equipment's serial port pinout matches IBM AT-AT null modem wiring before installation — non-standard pinouts on some console servers or serial terminal devices may require a different cable or adapter.
• This SKU is non-cancelable and non-returnable — order only after verifying cable length, connector gender, and null modem vs. straight-through wiring requirements against your actual hardware.

Best suited for IT teams maintaining legacy serial console access in data centers or equipment rooms where IBM AT-compatible serial hardware is still in the rack and a reliable 40-foot null modem run is needed for out-of-band management.