Description
AT&T 7400C-L1 DEFINITY High Speed Link Data Service Unit DSU
The AT&T 7400C-L1 is a desktop Data Service Unit (DSU) designed for use with AT&T DEFINITY PBX systems over dedicated digital data circuits. It provides the interface between the DEFINITY system's High Speed Link and the digital leased-line network, handling line conditioning, framing, and data conversion. Front-panel LED indicators (DTR, DSR, RD, SD, CTS, TT, RD) provide real-time line status monitoring, and a small LCD display with HOME, NEXT/NO, BACK, and ENTER/YES navigation buttons allows local configuration and diagnostics.
Specifications & What's Included
- Model: AT&T 7400C-L1
- Part Number: 106654478
- Product Line: DEFINITY High Speed Link
- Type: Data Service Unit (DSU)
- Form Factor: Desktop
- Front Panel: LCD display; LED indicators (DTR, DSR, RD, SD, CTS, TT, RD); POWER and DATA indicator lights; HOME, NEXT/NO, BACK, ENTER/YES navigation buttons
- Rear Panel: RJ-style line port; DB25 (25-pin) serial data connector; 4-pin power connector; multi-pin terminal block (77A data mounting interface)
- Required Power Supply: AT&T WP90110 L7 (not included — contact us to confirm availability)
- UL Listed: File 91B0
- FCC Compliance: Part 15, Class A Computing Device
- Compatible with AT&T 77A Data Mounting
- What's Included: DSU base unit only — no AC adapter
Applications
The AT&T DEFINITY High Speed Link DSU was developed in the late 1980s and early 1990s as a companion device for AT&T's DEFINITY enterprise PBX platform. It serves as the network termination point for high-speed data circuits, connecting the DEFINITY system to dedicated digital leased lines used for inter-site data communication and integrated voice/data networking. In DEFINITY installations, these units were typically deployed at customer premises to extend data connectivity between PBX locations or to link the PBX to central data networks. Organizations maintaining legacy AT&T DEFINITY G1, G2, or G3 systems — still found in some large enterprise and government environments — may require this DSU for continued High Speed Link operation or as a replacement spare. The unit's integrated status LEDs and local management interface made it straightforward to monitor line conditions and troubleshoot circuit issues without additional test equipment.
This AT&T 7400C-L1 DEFINITY High Speed Link Data Service Unit has been inspected and is in good condition. The case is clean with light surface wear consistent with normal office use. Front-panel buttons and the LCD display appear intact. The rear connectors, including the DB25 port and multi-pin terminal block, show no visible damage. Please note: no AC adapter is included. The required power supply is the AT&T model WP90110 L7; availability of a matching adapter is limited — contact us before purchasing if the adapter is essential. Please view our photo set and contact us if you have any questions. Please note: We have multiple units in stock — yours may not be the one shown in the photos, however, it will be similar in condition and function.
Warranty Information
Additional Information
Brand: |
AT&T |
Model: |
7400C-L1 |
MPN: |
7400C-L1 |
Secondary Model: |
106654478 |
SKU: |
11693 |
Type: |
Data Service Unit (DSU) |
Product Line: |
DEFINITY High Speed Link |
Compatible With: |
AT&T DEFINITY PBX Systems |
Power Supply Model: |
WP90110 L7 (not included) |
Data Mounting: |
77A Data Mounting |
Form Factor: |
Desktop |
FCC Compliance: |
Part 15, Class A Computing Device |
Seller Notes: |
No AC adapter included; AC adapter (WP90110 L7) may be available — contact us to confirm. |
Condition: |
Used – Inspected |
Country/Region of Manufacture: |
United States |
Condition Notes: |
AT&T 7400C-L1 DEFINITY High Speed Link DSU inspected and in good condition. Light surface wear. Rear connectors intact. No AC adapter (WP90110 L7) included — contact us to check availability. |
