Codex Motorola 8250 LDSU Limited Distance Modem DTE Desktop 115VAC 48250

Codex Motorola 8250 LDSU Limited Distance Modem DTE Desktop 115VAC 48250

The Codex Motorola 8250 LDSU is a desktop limited distance modem (LDM), also referred to as a short-haul modem, designed to extend digital data signals over dedicated two-wire or four-wire metallic circuits without the need for a telephone company-provided line. The 8250 LDSU (Limited Distance Service Unit) connects DTE equipment via its DB25 EIA-232 interface and transmits data over short-range leased or private line circuits. It is a product of Codex Corporation, a Mansfield, Massachusetts–based data communications manufacturer that became a Motorola subsidiary — both names appear prominently on the unit.

Specifications & What's Included

• Model: 8250 LDSU
• Product Code: 48250
• Manufacturer: Codex Corporation (Motorola), Mansfield, MA
• Form Factor: Desktop / tabletop enclosure (blue molded plastic)
• Power: 115VAC, 60Hz, 0.1A
• Fuse: 0.2A SLO BLO (rear panel, press-to-release fuse holder)
• DTE Interface: DB25 female (EIA-232 / RS-232), labeled DTE on rear panel
• Line Interface: Screw terminals — XMT (pins 1–2), GND (pin 3), RCV (pins 4–5)
• Front-panel LED status indicators: RTS, TD, RD/ER, DCD, RLB, TEST, PWR
• Internal DIP switch panel (accessed via front drop-down door): loopback configuration — OFF / DOWN positions
• UL Listed (File LR31546, Card 757C)
• Includes: power cord

Applications

Limited distance modems like the Codex 8250 LDSU were used to connect data terminal equipment (DTE) — such as minicomputers, mainframe front-end processors, and dedicated terminals — over short-range private or leased metallic lines, typically within a campus, industrial plant, or between nearby buildings. Unlike long-haul modems that operated over the public switched telephone network, LDMs transmitted baseband or low-frequency signals directly, making them faster and simpler for in-building or campus-range connections. The LDSU designation indicates it was designed for limited distance service applications, and its screw-terminal line interface was typical for permanent wired installations. Codex Corporation was a prominent player in data communications during the 1970s and 1980s, and units like this 8250 LDSU date from that era of synchronous and asynchronous serial data networking — before Ethernet-based LANs displaced dedicated point-to-point serial links. These units still see use today in legacy industrial, government, and utility environments where dedicated serial point-to-point circuits remain in service.