Cisco NM-4A/S 4 port serial for 2600 3600 3700 2610! The Cisco NM-4A/S is a 4 Serial network module. The 4-port (NM-4A/S) asynchronous/synchronous (async/sync) network modules provide async connectivity with speeds up to 115.2 kbps, and sync connectivity with speeds up to 128 kbps. These modules use the 60-pin "5-in-1" cables, similar to those used on the Cisco 2500 and Cisco 7000 series routers. You can use this card to make your router simulate a frame-relay switch!! This unit has been tested, and is in excellent working order.