(PSTN). THE PUBLIC SWITCHED TELEPHONE NETWORK (PSTN) Installing a video communication system requires some understanding of the circuit- switched public switched telephone network known as the PSTN. The PSTN is the set of digital dial-up services offered by carriers. It includes network-based services and network-based switching. The PSTN consists of analog and digital components. In order to identify what is analog and what is digital, we will divide the PTSN into three broad categories: access, switching, and transport. Access is the portion of the circuit that connects the customer's premises to the first network switching point. Another term used to refer to access is local loop. A local loop has two ends: the one that connects to the customer's equipment and the one that connects to the telephone company's (carrier) switching equipment. The switching equipment is said to reside in the carrier's central office or CO. Switching allows one Video Communications: The Whole Picture node to be connected to another node and is accomplished via addressing (in which an address is a telephone number). A circuit-switched connection can be made directly within the serving central office (if the same CO also serves the called party) or carried across the PSTN to a distant CO. The local loop is usually conditioned to provide analog transmission service (POTS). Most customers in the United States can buy, as an option, digital local access. The remainder of the PSTN is digital. CO switches are digital and the trunks that connect them are high-capacity digital facilities. Prior to 1996, only local exchange carriers (LECs), with a few minor exceptions, provided the local loop, in a monopoly arrangement. Although allowing monopolies to exist seems like a misguided practice, at the time that the U.S. PSTN was being constructed, this was really the only alternative. The Old PSTN In 1934, Congress passed the Communications Act. It created the Federal Communications Commission (FCC). The Act was intended to regulate the market for