Adtran DSU II AR J131C T1 DSU CSU RS-232 V.35 Primary Secondary Channel

Adtran DSU II AR J131C T1 DSU CSU RS-232 V.35 Primary Secondary Channel

The Adtran DSU II AR is a standalone T1 DSU/CSU (Data Service Unit / Channel Service Unit) designed for digital WAN connectivity over T1 lines. It provides both a Primary RS-232 port and a Primary V.35 port for DTE connections, a Secondary Channel port, and a Telco RJ48S interface for the network side. The front panel features a red LED display, TEST/STATUS/CONFIG indicators, a SCROLL dial, and CANCEL/ENTER buttons alongside PRI and SEC LED status rows for real-time line monitoring.

Specifications & What's Included

• Manufacturer: Adtran — Huntsville, AL
• Model: DSU II AR
• Part Number: J131C
• Type: T1 DSU/CSU (Data Service Unit / Channel Service Unit)
• Primary Interface 1: RS-232 (DB25)
• Primary Interface 2: V.35 (DB37)
• Secondary Channel port (DB25)
• Telco port: RJ48S (USOC Jack Type, FCC Part 68 compliant)
• Front panel: LED 4-digit display, TEST / STATUS / CONFIG LEDs, SCROLL dial, CANCEL / ENTER buttons
• PRI status LEDs: RS, CS, TD, RD, CD, TR, SR
• SEC status LEDs: CS, TD, RD
• Power: 115V AC, 60Hz
• Fuse: 2A, 250V, Type 3AG
• Form Factor: Desktop
• FCC Registration No.: HDCUSA-65263-DE-N
• Standards: FCC Part 68, USOC RJ48S, UL Listed (LR857, Information Processing Equipment)

Applications

DSU/CSU units like the Adtran DSU II AR serve as the interface between a customer's digital data equipment (DTE — routers, multiplexers, or frame relay access devices) and the T1 local loop provided by the telephone carrier. The DSU converts the customer device's RS-232 or V.35 serial data into the bipolar line format required on a T1 circuit, while the CSU function terminates the line, handles loop-back testing, and ensures compliance with FCC Part 68 and ANSI T1.403 requirements. Units with both RS-232 and V.35 primary ports — like the DSU II AR — were common in enterprise and campus WAN environments of the 1990s and early 2000s, where they connected PBX systems, routers, video conferencing equipment, and frame relay access devices to carrier T1 services. The Secondary Channel port adds a drop-and-insert capability for splitting off a portion of the T1 bandwidth to a separate device. The Adtran DSU II AR was a well-regarded mid-range unit in its era and is still sought by technicians maintaining legacy T1 infrastructure or needing a parts source for the DSU II AR platform.