Allen Tel Products GB183A1 Blue Backboard Assembly Half Module 8.5x20 4S66MI-50

Allen Tel Products GB183A1 Blue Backboard Assembly Half Module 8.5x20 4S66MI-50

The Allen Tel Products (ATP) GB183A1 is a half-module blue backboard assembly measuring 8.5 inches by 20 inches, designed to mount telephone connecting blocks in key telephone system wiring installations. It comes equipped with four GB89D brackets that provide vertical jumper channels aligned to the GB20 Distributing Ring positions used on GB184 and GB187B1 full-size backboards.

Specifications & What's Included

• Manufacturer: Allen Tel Products, Inc. (ATP)
• Part Number: GB183A1
• Description: Backboard Assembly, Half Module — Blue
• Dimensions: 8.5 in x 20 in
• Color: Blue
• Module Size: Half Module
• Brackets: 4x GB89D mounting brackets (installed)
• Compatible Connecting Blocks: 4x S66MI-50 (200-pair capacity) or 4x S66MI-25 (100-pair capacity)
• Cable Capacity: Supports termination of up to 8 x 25-pair cables
• Compatible Full Backboards: GB184, GB187B1
• Compatible Distributing Ring: GB20
• Application: Key Telephone Systems

Applications

The GB183A1 backboard is used in structured telephone wiring installations for key telephone systems (KTS), where S66-type connecting blocks are the standard cross-connect and termination hardware. The GB89D brackets mounted on this backboard create vertical jumper channels that line up with the GB20 Distributing Ring positions on larger GB184 and GB187B1 backboards, allowing organized routing of jumper wires between blocks. This type of backboard is a standard component in telephone equipment rooms and wiring closets, particularly in commercial and light-industrial settings that use 25-pair building cable infrastructure. The half-module format of the GB183A1 is used when a full-size backboard is not needed, or when space must be shared with other equipment. S66 block systems were widely deployed through the 1980s and 1990s and remain in service in many legacy telephone installations maintained today.