A device that interfaces an analog device to a digital circuit or channel. Codecs operate in balanced and symmetrical pairs, with one at each end of the communications circuit and with both having the same capabilities, at least at a minimum level. On the transmit side of the connection, a codec accepts an incoming analog signal, encodes it (i.e., converts it into digital form), and places it on a digital circuit. On the receive side of the connection, a codec with matching capabilities accepts the digital signal and decodes it to (i.e., recreates) an approximation of the original analog signal. Many codecs are capable of operating in full duplex (FDX), simultaneously encoding signals as they transmit them and decoding signals as they receive them. See also analog, channel, circuit, digital, encode, and FDX.