Cisco 28-1620-03 Serial V.35 WAN Interface Module Plug-In Card Networking

Cisco 28-1620-03 Serial V.35 WAN Interface Module Plug-In Card Networking

The Cisco 28-1620-03 is a Serial V.35 WAN Interface plug-in module designed for use in Cisco networking enclosures. It provides a V.35 serial interface for connecting to WAN equipment such as DSU/CSUs, multiplexers, and leased-line service devices, enabling serial WAN connectivity within compatible Cisco router or enclosure platforms. The module slots directly into a supported Cisco chassis, adding dedicated serial WAN port capacity.

Specifications & What's Included

• Manufacturer Part Number (MPN): 28-1620-03
• Interface Type: V.35 Serial
• Form Factor: Plug-In Module (card with integrated mounting bracket)
• Connectors: V.35 serial connectors visible on module edge
• PCB includes multiple logic ICs and two large controller/processor chips
• Compatible with: Cisco networking enclosures supporting serial WAN interface modules
• Module only — no cables or additional accessories included

Applications

The Cisco 28-1620-03 Serial V.35 module is used to add serial WAN connectivity to Cisco modular routers and networking enclosures. V.35 is a widely adopted ITU-T interface standard for high-speed synchronous serial data communication, commonly used to connect routers to WAN service equipment including T1/E1 DSU/CSUs, frame relay access devices, and synchronous modems. These plug-in interface modules were a core part of Cisco's modular router architecture from the mid-1990s onward, allowing network administrators to customize WAN port configurations by installing the appropriate interface cards into a shared chassis. Serial V.35 interfaces remain relevant in legacy WAN environments, leased-line installations, and industrial or government networks that continue to use synchronous serial WAN links.