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. Shipping via UPS Ground in the USA plus any COD fees. International shipping available at an extra cost.