is a type of mux that consolidates the indi- vidual channels: 24 channels are associated with T-1, and 32 channels are associated with E-1. These voice and data channels are 64Kbps each, and they can be aggregated onto a higher-speed transmission line. Channel banks were designed to accept analog input, so if there is an analog switch either at the PBX or at the local exchange, that analog signal can be digi- tized, using Pulse Code Modulation (PCM), as described in Chapter 4. The channel banks provide a first level of aggregation. Beyond that, the cus- tomer might want to migrate to higher bandwidth, which would involve using T-1/E-1 or T-3/E-3 multiplexers. (Refer to Chapter 4 for a description of the rates associated with the various digital signal levels.) Intelligent multiplexers are the most important equipment in building the enterprise backbone network because they act dynamically to manage transmis- sion resources. They allow you to make on-the-fly decisions about who is allocated the capacity, how much capacity needs to be allocated to each user, and whether individual users have rights to access the resource they want to access. In Figure 7.7, the intelligent muxes basically form a smart computer. An intelligent mux has a port side to which you interface the universe of information resources, which could Intelligent Mux Videoconferencing Voice Trunk T-1/E-1/J-1 LAN Adapters Routers Frame Relay T-1/E-1 trunks to other T-1/E-1 muxes Figure 7.7 T-1/E-1 and T-3/E-3 muxes Chapter 7 Wide Area Networking be the videoconferencing systems, or the voice systems, or the variety of data uni- verse that you have. On the trunk side, you terminate the T-1s/E-ls or T-3s/E-3s. Inside the muxes are databases that allow you to make decisions in real-time. One of the greatest benefits of managing your own bandwidth between locations that you can use that bandwidth as you need it. There are two ways you can use T-, E-, or J-carrier facilities. First, you can use them as an access pipe. For example, you can use a T-1 to acc