A modem designed to support high speed data communications over hybrid fiber/coax (HFC) CATV networks. Cable modems are positioned at the customers' premises and in a cable modem termination system (CMTS) at the service provider's headend. The initial Data over Cable Service Interface Specification (DOCSIS), released in 1997, standardized cable modems. Continuing research and development efforts directed at cable modems and related CATV network standards are largely the responsibility of CableLabs. See also CableLabs, CATV, CMTS, DOCSIS, HFC, and modem.