 wanting digital service. Switched 56 Service Although switched 56 service has become a relic, we will discuss it because it is still Circuit-switched Networks used and it was one of the original enabling telecommunication technologies for videoconferencing. The IXCs and LECs offer switched 56 dial-up digital service. It non-standards-based digital adaptation of a regular telephone line, which means it uses in-band signaling. As its name implies, it allows customers to call up and transmit digital information at speeds up to 56 Kbps, using regular dialing techniques. Switched 56 service is billed like a voice line-e.g., a monthly charge plus a cost for each minute of usage. AT&T was first to offer switched 56, in 1985, when LECs offered no comparable form of switched digital access. Most carriers, including MCI, and Sprint, developed a switched 56 offering. Even though it is not standards-based, any two customers who use LEC-provided switched 56 service can interconnect, even when an IXC crosses a LATA line. H.323 H.323 Public Workstation Workstation Switched Telephone Network H.323 Workstation Internet Ethernet H.320 H.323 IP Phone Workstation Workstation Router H.323 Workstation Ethernet Gateway Switch Ethemet H.323 Gatekeeper Database Application H.323 Server Server Workstation Multipoint Control Unit Fileserver H.323 IP Phone Workstation Figure 11-2. In-Band Vs. Out-Of-Band Signaling (Laura Long). In most switched 56 videoconferencing applications, two channels are aggregated to yield one 112 Kbps circuit. This is bare-minimum bandwidth for group-system videoconferencing but many organizations get by with it. Organizations that want the freedom to call anyone, regardless of which long distance carrier serves them, use the LEC's switched 56 lines (or, more commonly now, ISDN BRI) to reach an IXC's switched 56 service. Users of switched 56 (using Video Communications: The Whole Picture either switched or dedicated access) can place calls to ISDN customers, as long as the ISDN equipment can accept switched 56 ca