CRC IDRU-II Intelligent Digital Recovery Unit Modem 120VAC DCE DTE RS-232

CRC IDRU-II Intelligent Digital Recovery Unit Modem 120VAC DCE DTE RS-232

The CRC IDRU-II (Intelligent Digital Recovery Unit) is a desktop modem and dial-backup device made by Control Resources Corporation of Paramus, NJ. It is designed to monitor a primary data circuit and automatically switch to a dial backup path when the primary line fails, restoring communications without manual intervention. The front panel provides LED status indicators for POWER, TD, RD, DTR, RTS, CTS, DIAL LINE, BACKUP, and FAULT conditions, plus a seven-segment STATUS CODE display and a BACKUP ACTIVATE/DEACTIVATE control for manual override.

Specifications & What's Included

• Manufacturer: Control Resources Corporation (CRC), Paramus, NJ
• Model: IDRU-II (IDRU Series Modem)
• Secondary designation: CONT/RES2
• Power: 120 VAC, 0.20A, 50/60Hz
• Form factor: Desktop / tabletop enclosure
• Front panel indicators: POWER, TD, RD, DTR, RTS, CTS, DIAL LINE, BACKUP, FAULT LEDs
• Front panel: Red 7-segment STATUS CODE display; BACKUP ACTIVATE/DEACTIVATE button
• Rear ports: TO DCE (DB-25) and TO DTE (DB-25) data interfaces
• Rear connections: TEL LINE jack, POWER inlet
• Rear controls: RESET / SELF-TEST button
• Certifications: UL Listed Telephone Equipment (4C74); Communications Canada 730 5248 A
• Unit only — no cables or accessories included

Applications

The IDRU series was designed for use in leased-line and private-line data communications networks, typically in enterprise, banking, and industrial environments where an uninterrupted WAN connection was critical. When the primary leased line went down, the IDRU would automatically dial a backup PSTN path and restore the data link, then drop back to the primary when it recovered — a function known as dial backup or automatic line recovery. Units like this were commonly used with RS-232 DTE equipment (terminals, computers, controllers) and DCE modems to bridge a site back to a central host or network during outages. The IDRU-II dates from the 1980s to early 1990s, the era when leased analog and digital lines formed the backbone of wide-area corporate networking before frame relay and the modern internet became widely available. Today these units are sought by legacy network maintainers, industrial control system operators running older infrastructure, and collectors of vintage telecom equipment.