 that affects IP/UDP/RTP headers. CSD (Circuit-Switched Data) The original form of data transmission developed for TDMA-based mobile phone systems such as GSM. CSMA (Carrier Sense Multiple Access) A LAN access technique in which multiple sta- tions connected to the same channel can sense transmission activity on that channel and defer the initiation of transmission while the channel is active. CSMA is similar to contention access. Glossary CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) A scheme for con- trolling network traffic that enables any of multiple nodes to send information over a shared net- work cable if the cable is free. It avoids collisions by having all nodes signal their intention to transmit before transmitting. If two nodes send intentions to transmit messages at the same time, both nodes wait for random amounts of time before trying again. CSMA/CD (Carrier Sense Multiple Access/Collision Detection) A LAN protocol that is a refinement of CSMA in which stations can detect the interference caused by simultaneous transmissions by two or more stations (collisions) and retransmit colliding messages in an orderly manner. (channel service unit) A component of CPE used to terminate a digital circuit, such as a leased line or T-1/E-1 facility, at the customer site. A CSU performs certain line-conditioning functions and responds to loopback commands from the local exchange. It also ensures proper 1s density in a transmitted bitstream and performs bipolar violation correction. CTS (clear to send) A control circuit that indicates to the DTE that data can or cannot be transmitted. customization The process of designing or configuring a device, installation, or network to meet the requirements of particular users. cutover The physical changing of lines from one system to another, usually at the time of a new system installation. CVSD (Continuous Variable Slope Delta Modulation) A speech encoding and digitiz- ing technique that uses 1 bit 