Archives

Compiled by Ron Hranac, CT Senior Technology Editor

CATV: Originally "community antenna television," the term today generally is accepted to mean simply "cable TV."

CMTS: Cable modem termination system. A device located in a cable operator's headend or hub site, the CMTS provides the interface between the cable television RF network and data equipment connected to the Internet.

CSU/DSU: Channel service unit/digital service unit. A device that functions as remote access test equipment to determine whether potential problems are in the headend or in the circuit to the Internet.

DBS: Direct broadcast satellite. A Ku-band satellite service that broadcasts multiple channels of TV, audio and data from satellites to pizza-size dish antennas.

DOCSIS: Data Over Cable Service Interface Specification. An international standard for cable modems and related equipment.

Downstream: The signal transmission path from the cable company's headend to the cable subscriber. In sub-split CATV networks, the downstream spectrum ranges from 50 MHz to as high as 860 MHz.

DSL: Digital subscriber line. This is technology that allows high-speed data transmission over conventional copper telephone lines.

Headend: A central receiving, processing and distribution facility in a cable network. Somewhat analogous to a telephone company's central office, the headend receives signals from over-the-air broadcast, satellite and local studio sources. The signals are processed, converted to TV channels that can be carried on the cable network, combined and transmitted over optical fiber and/or coaxial cable.

HFC: Hybrid fiber/coax. A cable TV network architecture that uses a combination of fiber optics and coaxial cable technology for signal transportation and distribution.

IEEE: Institute of Electrical and Electronics Engineers, Inc.

IP: Internet protocol. One of two major protocols used in internetworking.

kbps: Kilobits per second. A data transmission rate of one thousand bits per second.

LAN: Local area network. Any physical data network technology used to cover short distances, typically up to a few thousand meters.

Mbps: Megabits per second. A data transmission rate of one million bits per second.

MCNS: Multimedia Cable Network System Partners Limited. The consortium that developed the Data Over Cable Service Interface Specification (DOCSIS). The specification later became an international standard under the auspices of the International Telecommunications Union.

MMDS: Multichannel multipoint distribution service. An over-the-air microwave service that transmits multiple channels of TV, audio and data to paying subscribers. Sometimes called wireless cable.

MSO: Multiple system operator. A cable company that owns or manages more than one cable TV system.

NIC: Network interface card. A plug-in card for a personal computer that provides an external 10Base-T or 10/100Base-T Ethernet connection.

PC: Personal computer

PCI: Peripheral component interconnect. Interconnection system between a personal computer's microprocessor and related devices, usually via expansion slots on the PC's motherboard.

PRI: Primary rate interface. An integrated services digital network (ISDN)-based network service, typically provided by the local telephone company. A PRI circuit comprises 23 B-channels and one 64 kbps D-channel using a 1.544 Mbps T1 line.

PSTN: Public switched telephone network. A general term for the telephone company's network.

QAM: Quadrature amplitude modulation. A method of modulating digital data onto an RF carrier by varying both the phase and amplitude of the carrier.

QPSK: Quadrature phase shift keying. A method of modulating digital data onto an RF carrier by varying the phase of the carrier.

RBOC: Regional bell operating company. After the 1980s breakup of AT&T, seven regional telephone companies were created. Each of these companies was called a regional bell operating company.

RF: Radio frequency. Generally refers to electromagnetic signals higher than about 100 kHz to 300 kHz in frequency, but below the frequency of infrared light.

Telco: A shorthand term that means telephone company.

UPS: Uninterruptible power system; also uninterruptible power supply.

Upstream: The signal transmission path from the subscriber to the cable company's headend. In sub-split CATV networks, the upstream RF spectrum ranges from 5 MHz to as high as 42 MHz.

USB: Universal serial bus. A so-called plug-and-play interface between a personal computer and external devices, such as digital cameras, printers, scanners, external disk drives and so forth.

Ron Hranac is a consulting systems engineer for Cisco Systems, and senior technical editor for Communications Technology. You may reach him at .

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