See Asterisk Channel Bank for help with setting up Asterisk with channel banks.

A channel bank is a device at a telephone company central office (public exchange) that converts analog signals from home and business users into digital signals to be carried over higher-speed lines between the central office and other exchanges. The analog signal is converted into a digital signal that transmits at a rate of 64 thousand bits per second (Kbps). This 64 Kbps signal is a standard known as a DS0 signal. The signal is multiplexed with other DS0 signals on the same line using time-division multiplexing ( TDM ) . Usually, the digital information is put on each DS0 signal using pulse code modulation (PCM). The channel bank is the foundation for all digital telecommunication transmissions. It is the part of a carrier -multiplex terminal that multiplexes a group of channels into a higher bit-rate digital channel and demultiplexes these aggregates back into individual channels. A channel bank changes analog voice and data signals into a digital format. It is called a "bank" because it can contain enough processing power to convert a bank of up to 24/32 individual channels to a digital format, and then back to analog again. The 24/32 channels comprise a T1/E1 circuit. A channel bank can also multiplex a group of channels into a higher bandwidth analog channel.

Modern channel banks have a small foam factor of about 60 channles per a shelf (19" * 3U), supports variants CAS, any combination of multiple FXO/FXS cards, a line characteristics(R, L, C) measuring card, a remote management card with SQL backended GUI, and two redundant DC power modules. All cards and modules should be hot plugable without affecting any functionality of other.