Cisco's Packet-over-T3/E3 network module for the Cisco 2600, 3600, and 3700 series offers the first software-configurable T3/E3 product from Cisco. This flexible network module allows the customer to switch between T3 and E3 applications with a single Cisco IOS command. This feature provides customers with unparalleled investment protection by allowing the service provider or enterprise customer to stock only a single product that can be deployed internationally. The demand for increased bandwidth has led to growth in clear-channel T3/E3 deployment. This new Packet-over T3/E3 network module (part number NM-1T3/E3) eliminates the need for an external data service unit (DSU), reduces provisioning costs, and provides highly manageable T3/E3 line termination. The module provides an integrated line interface unit (LIU) DSU that allows T3 or E3 lines to be directly terminated on a Cisco router, eliminating the need for external DSU equipment. This simplifies the T3/E3 line management, reduces provisioning cost, and frees valuable rack space. Offering unprecedented flexibility in provisioning clear-channel T3 or E3 connections, the Cisco T3/E3 network modules provide support for the proprietary subrate and scrambling features of T3 DSU vendors Digital Link, Larscom, and ADC Kentrox. Subrate support in the Cisco T3/E3 Network Module maximizes the utility of these products in service provider environments for tiered DS3 services. By simultaneously supporting interoperability with a wide range of third-party DSU vendors, this network module offers the flexibility to support installed equipment without locking customers into a proprietary solution. The Cisco T3/E3 Network Module provides direct connectivity to a T3 line for full-duplex communications at the T3 rate of 44.736 MHz and full-duplex E3 communications at 34.368 MHz. Each T3 or E3 port consists of a pair of 75-ohm BNC coaxial connectors (Type RG-59), one for transmit data and one for receive data, along with six LED indicators for line status. The Cisco 2650XM and 51XM, Cisco 2691, Cisco 3660, and the Cisco 3725 support a single T3/E3 network module. The Cisco 3745 supports up to two single-port Cisco T3/E3 network modules. Because the Cisco T3/E3 Network Module is supported in Cisco IOS feature sets, including IP Only, there are no additional memory requirements for any supported platforms.