ision derived from the SMPTE RP125 and EBU 324E standards. It uses a 4:2:2 sampling scheme for Y, U and V with luminance sampled at 13.5 MHz and chrominance (U and V components) sampled at 6.75 MHz. After sampling, 8-bit digitizing is used. The particular frequencies set forth in the standard were chosen because they work for both 525/60 (NTSC) and 625/50 (SECAM and PAL) television systems. In the US the system specifies that 720 pixels be displayed on 243 lines of video and that 60 interlaced fields be sent per second. Chrominance channels are sent with 360 pixels on 243 lines, again at 60 fields/second. CCIR Recommendation 601 is used in professional digital video equipment. Common Channel Inter-Office Signaling. In this scheme, which is used for ISDN, the signaling information is carried out-of-band over a special packet-switched signaling channel. CCITT Abbreviation of Comité Consultatif International Téléphonique et Télégraphique, an organization that sets international telecommunications standards. The CCITT is now called the International Telecommunications Union's Telecommunications Standardization Sector or ITU-T. Closed circuit television. Typically used in security and surveillance applications and usually based on slow-scan technology. A high-capacity optical storage device that measures 4.75-inch in diameter and which contains multimedia or audio-only information. Originally developed for sound, CD technology was quickly seen as a storage medium for large amounts of digital data of any type. The information on a CD is digitally encoded in the constant linear velocity (CLV) format, which replaced the older CAV (constant angular velocity) format. Philips Compact Disc-interactive specification, which embraces the same storage concept as CD-ROM and Audio CD, except that CD-i also stores compressed Video Communication: the Whole Picture full-motion video. CD-ROM Compact Disc Read-Only Memory. A standard used to place any type of digital data onto a compact disc. Compression Labs Compressed Digital Video, 