IBM 5865-2 56X3250 Modem Synchronous Async Leased Line Desktop 120V 1986

IBM 5865-2 56X3250 Modem Synchronous Async Leased Line Desktop 120V 1986

The IBM 5865-2 is a desktop synchronous/asynchronous modem designed for leased-line data communications in IBM midrange computing environments. Part number 56X3250, it features a front-panel LED status display and a full hexadecimal keypad for local and remote configuration, diagnostics, and line monitoring — all without a separate terminal. Manufactured by IBM Corporation in 1986.

Specifications & What's Included

• Manufacturer: IBM Corporation, Armonk, New York
• Model: 5865-2
• Part Number: 56X3250
• Type: Synchronous / Asynchronous Leased-Line Modem
• Form Factor: Desktop (standalone tabletop unit)
• Power: 120V AC, 0.62A, 50/60Hz, 0.08 kVA
• Year: 1986 (IBM Corp. copyright date on rating label)
• Front Panel: Green LED status/indicator display bar (Address, LG, Oper, RTS, RFS, TD, CD, RD)
• Front Panel Keypad: LOC / REM / TEL rows; hex keys 0–F with labeled functions (Test, Status, Speed, Conf, Anlg, Dgtl, Bckup, Cmd, Call, Dial, Disc, Loop); Go / Erase / Exit / Stop control keys
• Rear Connectors: DB25 (parallel/data interface), DB9 serial port, proprietary expansion slot openings, IEC AC power inlet
• Certifications: UL Listed 167G E.D.P. Equipment; FCC Part 15 Class A Computing Device
• Includes: IBM 5865 and 5866 Modems Reference Card (Publication No. GA33-0080)

Applications

The IBM 5865 series modems were developed for leased private-line data communications connecting IBM midrange systems — including the System/36, System/38, and early AS/400 — to remote terminals, controllers, and host systems over dedicated analog circuits. Unlike dial-up modems, leased-line modems operate on permanently connected circuits, providing the consistent, low-latency links that IBM's synchronous data link control (SDLC) and bisynchronous (BSC) protocols required. The front-panel keypad was a distinctive IBM feature that allowed operators to run local and remote loopback tests, check line status, switch between analog and digital test modes, and configure the unit without a separate configuration terminal. The 5865-2 dates from the mid-1980s era of IBM SNA (Systems Network Architecture) networking, when dedicated leased lines were the standard way to connect branch offices and remote sites to central IBM mainframe and midrange hosts. Today these units are primarily sought by collectors of vintage IBM computing equipment, museums, and organizations maintaining legacy IBM midrange infrastructure.