ata. ATM is a dedicated- a common signaling channel for all the voice channels. connection switching technology that organizes digital Primary Rate Interface for ISDN is the most typical data into 53-byte cell units and transmits them over example of this common channel signaling (CCS). If a physical medium using digital signal technology. voice/data integration is to be successful, all of these Individually, a cell is processed asynchronously relative voice interfaces must be supported to provide the widest to other related cells and is queued before being possible range of applications. Over the years, users have multiplexed over the transmission path. Because ATM grown to expect a certain level of performance, re- is designed to be easily implemented by hardware liability, and behavior of a telecommunications system, (rather than software), faster processing and switch which must be supported while going forward. All these speeds are possible. The pre-specified bit rates are issues have been solved by various packet voice systems either 155.520 Mbps or 622.080 Mbps. Speeds on ATM today SO that users can enjoy the same level of support to networks can reach 10 Gbps. Along with Synchronous which they have become accustomed. Before we jump Optical Network (SONET) and several other technol- into ATM, Frame Relay, and IP, we need to step back and logies, ATM is a key component of broadband ISDN take a look at TDM. (BISDN). From the start, ATM was designed to be a multimedia, multiservice technology. It has been accepted by the marketplace for its ability to deliver high-speed data ser- Time division multiplexing vices. Until the recent past, its potential for deploying for voice services was overlooked. With the competitiveness TDM is a scheme in which numerous signals are com- of today's market, the network operators and the service bined for transmission on a single communications line or providers have been continuously striving to reduce op- channel. Each signal is broken up into many segments, erating costs an