Description
Adtran ISU 128 1200.029L2 ISDN BRI U-Interface Terminal Adapter w/ V.35 Cable
The Adtran ISU 128 is a combined ISDN NT1 (Network Termination 1) and terminal adapter in a single desktop unit, designed to connect DTE equipment to a North American ISDN Basic Rate Interface (BRI) U-Interface line using the 2B1Q line code standard. Part number 1200.029L2, it bridges the ISDN U-Interface from the telephone company to serial DTE interfaces — specifically V.35, RS 530A, and RS 366 — making it suitable for connecting routers, videoconferencing equipment, and other serial-interface DTE devices directly to an ISDN BRI circuit without requiring a separate NT1 device.
Specifications & What's Included
- Manufacturer: Adtran, Huntsville, AL
- Model: ISU 128
- Part Number: 1200.029L2
- WAN Interface: ISDN BRI U-Interface, 2B1Q line code (North American standard)
- WAN Ports: Two RJ-style ports — DIAL and LEASED
- Serial DTE Interface: V.35 (34-pin Winchester connector)
- Additional Serial Interfaces: RS 530A (DB-25), RS 366 (DB-25)
- Front Panel: Backlit LCD display showing device status; LED indicators — RS, CS, TD, RD, CD, TR, SR
- Front Panel Controls: Numeric keypad (0–9, *, #) with ENTER and CANCEL keys
- Power: 110 VAC, 60 Hz, 0.07A
- Power Switch: Rear ON/OFF rocker
- Form Factor: Desktop
- Certifications: UL Listed (E130853), Industry Canada (2250 6145 A), FCC Part 15
- Includes: V.35 connection cable (34-pin Winchester, full length) and AC power cord
Applications
The Adtran ISU 128 was designed for late-1990s enterprise and small-business ISDN deployments in North America, where ISDN BRI (128 Kbps bonded, or 64 Kbps per B-channel) was widely used for digital WAN connectivity, videoconferencing, and dial-on-demand router links before broadband became ubiquitous. By integrating the NT1 and terminal adapter functions in a single chassis, the ISU 128 eliminated the need for a separate NT1 box — simplifying installation at customer premises. The V.35, RS 530A, and RS 366 serial interfaces allowed direct connection to routers (such as Cisco and Adtran's own Atlas and Total Access series), videoconferencing codecs, and inverse multiplexers that used those standard serial WAN interfaces. The RS 366 port provided automatic calling functionality for dial-on-demand applications. Today the ISU 128 is primarily sought by organizations maintaining legacy ISDN infrastructure, by technicians supporting older videoconferencing or point-of-sale systems that remain on ISDN circuits, and by collectors of late-1990s telecom equipment.
This Adtran ISU 128 ISDN terminal adapter (P/N 1200.029L2) has been pulled from a working environment and is in used condition. The unit powers on — the front-panel LCD and LED status indicators are active in the photos. The plastic housing shows the yellowing typical of equipment from this era, and there is light general wear consistent with normal use. The rear connectors (V.35, RS 530A, RS 366, and the ISDN RJ ports) appear clean and undamaged. Included with the unit are the V.35 connection cable and the AC power cord, both of which are visible in the photos. Please view our photo set and contact us if you have any questions.
Warranty Information
Additional Information
Brand: |
Adtran |
Model: |
ISU 128 |
MPN: |
1200.029L2 |
Type: |
ISDN BRI Terminal Adapter / NT1 |
SKU: |
39524 |
Interface Type: |
ISDN BRI U-Interface (2B1Q) |
Serial Interface: |
V.35, RS 530A, RS 366 |
WAN Interface: |
ISDN U-Interface (2B1Q), Dial and Leased |
Number of WAN Ports: |
2 (DIAL, LEASED) |
Power Requirements: |
110 VAC, 60 Hz, 0.07A |
Form Factor: |
Desktop |
Display: |
LCD with LED status indicators (RS CS TD RD CD TR SR) |
Keypad: |
Numeric keypad with ENTER and CANCEL keys |
Certifications: |
UL Listed (E130853), Industry Canada 2250 6145 A, FCC Part 15 |
Country/Region of Manufacture: |
United States |
Seller Notes: |
Includes V.35 cable and AC power cord |
Compatible With: |
ISDN BRI U-Interface (North America 2B1Q) lines |
Compatible With 2: |
V.35, RS 530A, RS 366 DTE equipment |
Condition Notes: |
This Adtran ISU 128 ISDN terminal adapter (P/N 1200.029L2) was pulled from a working environment. Unit powers on; LCD and LEDs are active. Housing shows age-related yellowing and light wear. Includes V.35 cable and AC power cord. |
California Prop 65 Warning: |
WARNING: This product can expose you to chemicals including lead and lead compounds, and DEHP (a phthalate), which are known to the State of California to cause cancer and birth defects or other reproductive harm. Go to P65Warnings.ca.gov |
