l signals to the requirements of the digital networks that transport them. As the term implies, compression/decompression and coding/decoding are a codec's most important jobs. A codec must first turn analog signals into a continuous stream of zeros and ones (coding or digitizing), and then sort out the trivial bits from the ones that will be necessary for the session (compression). Because video requires an uncompressed digitized telephone signal with a network transmission speed of at least 90 million bits per second (Mbps), it is easy to appreciate the job of a codec. Even after discarding the vertical and horizontal synchronization information that analog television signals require, an uncompressed digitized television signal requires at least 45 Mbps. Contrast this with a common modem's pseudo 56 Kbps (kilobits per second), and one comprehends that the uncompressed signal's bandwidth requirements are substantial. To squeeze full- motion video plus audio over such a line (having captured that signal using some type of standard camera and microphone) would require the discard of 99.99% of the information. Even with a common cable modem or DSL line for transmission, the compression burden would be enormous. Today we can squeeze a sufficient videoconference over two ISDN (Integrate Services Video Communications: The Whole Picture Digital Network) B channels. We can squeeze a somewhat degraded version of the same signal over a plain old telephone service (POTS) line, the type of line that connects the vast majority of residential customers and many business telephone users to the public switched telephone network (PSTN). In 1978, the same degree of picture resolution and motion handling required six Mbps of bandwidth. A coast-to-coast line that connected corporate video communication facilities rented annually for about $35,000. Furthermore, in addition to the $250,000 codec we mentioned earlier, a company in the early 1980s had to buy cameras, microphones, and speakers, and prepare a conference facility to offer