The Old CATV Equipment Museum
Glossary of terms used on this website
Balun. A passive electronic device that converts a balanced electrical signal to an unbalanced signal, or vice versa. For the general-case definition, see Wikipedia. For the purpose of this website, a balun converts a 75-ohm balanced RF signal to an unbalanced 300-ohm signal:
BNC Connector. A coaxial cable connector available in 50- and 75-ohm configurations. The 75-home version of this connector was once used by some CATV equipment manufacturers for RF signal transmission, although it was ill-suited for this purpose due to cost and possible impedance mismatch; consequently, it was phased out after the introduction of C-Connectors and F-Connectors. This connector is universally used today for video and sync signals by the video production and broadcast industries, and it is still widely used for video signals by the cable TV industry.
Broadcast. For the purposes of this website, this term refers to the transmission of programming by a radio or television broadcast station holding a construction permit or license issued by the FCC pursuant to Part 73 or 74 of the
Code of Federal Regulations. This term does not refer to point-to-multipoint transmission via a ground-based network.
CATV. Cable Television. When this term was first coined, it stood for "Community Antenna Television," reflecting the nature of the business at the time: a single antenna system feeding multiple customers by means of a cable network. Over the years, as systems began carrying non-broadcast programming, the term became "Cable Television." Cf. MATV, SMATV.
C-Connector. An early type of threaded 75-ohm connector used on certain cable TV equipment; similar to the F-connector but having a smaller outside diameter. Like the F-Connector, the center conductor of the coaxial cable served as the connector center pin. Thread: 1/4-28. Not to be confused with the connector of the same name available today for use with 50-ohm RG8 and larger coaxial cables.
|Photos: Lew Chandler|
Channel designator. The numeric or alphabetic designation of a cable television channel. See Cable Television Analog Channel Designations.
Characteristic impedance. A property of a uniform transmission line, usually written Z0. It is determined by the geometry and materials of the transmission line and, for a uniform line, is not dependent on its length. Wikipedia.
Coaxial cable. See Wikipedia. Coaxial cable was first patented in 1880 by English inventor Oliver Heaviside but did not actually exist as a commercial product for nearly 50 years. For the purposes of CATV distribution networks, the most common types of coaxial cable used are:
Drop cable: A type of cable utilizing a solid cooper center conductor surrounded with a flexible shield composed of thin aluminum foil and/or wire mesh. The shield is typically covered with an outer protective sheath of plastic. Examples: types RG-59 and RG-6.
Trunk and feeder cable: A type of cable utilizing solid copper (or copper-clad aluminum) surrounded with a solid aluminum shield. The shield is typically covered with an outer protective sheath of plastic. Steel armor be used to provide additional protection for cables intended for direct burial.
dB. Decibel. See Wikipedia. This term is used to state the relative difference between two signal levels without reference to any specific level. Use of this term as a synonym for dBm or dBmV is erroneous.
dBj. dBmV, as originally defined by Jerrold. Apparently, Jerrold's competitors didn't approve of Jerrold's attempt to name this unit after itself.
dBm. Power ratio in decibels (dB) referenced to one milliwatt (mW). From the definition of the difference, in dB, between two power levels:
We define dBm as follows:
From which it follows that:
dBmV. Voltage ratio in decibels (dB) referenced to one millivolt (mV). From the definition of the difference, in dB, between two voltage levels:
We define dBmV as follows:
From which it follows that:
Detent Tuner A 12-channel tuner commonly used in consumer television receivers manufactured during the 1960s and 70s. It was designed to accept twelve standard NTSC television channels (usually VHF Channels 2-13), tune to the desired channel, and output the signal at the intermediate frequency. The mechanical design allowed the user to select a desired channel by rotating a knob; at each channel, a detent on the tuner shaft locked the shaft into position. Prior to the enactment of the All-Channel Television Act in 1962, most consumer television sets were equipped with a detent tuner capable of tuning only the VHF television channels 2-13. Following the enactment of the act, which required that all consumer television sets be capable of tuning UHF channels 14-83 as well as the VHF channels 2-13, most consumer TV sets were manufactured with two tuners: a detent tuner for VHF channels 2-13 and a continuous-tuning UHF tuner for the UHF channels.
F-Connector. An inexpensive threaded 75-ohm coaxial cable connector universally used by the cable TV industry for drops and inside wiring. This connector is also commonly used as an RF connector on consumer electronics equipment. Thread: 3/8-32. When properly installed and correctly tightened ("finger-tight plus 1/8 turn"), this connector provides excellent RF shielding.
|Photos: Neal McLain|
F-connectorized-C connector. A chassis-mounted female C-connector modified by the addition of a threaded 3/8-32 sleeve to make it compatible with male F-connectors. This connector was originally developed by Jerrold as a temporary measure before it started using true F-Connectors. According to Lew Chandler, the threaded sleeve provided structural support for the fragile C-Connector. Chandler further notes that this connector resulted in degraded frequency response.
Gonset Line. Trade name for 450-ohm ladder line formerly manufactured by Gonset Company of Burbank, California. The company no longer exists, but historical information may be found here.
Jones Connector. A multipin connector manufactured by Cinch Connectors, Inc. A six-pin Series 300 Jones Connector is used in the Jerrold Model 704 Series SLMs to carry power.
Ladder Line. Unshielded two-conductor transmission line used for the transmission of balanced radio frequency signals. The physical dimensions (conductor diameter and conductor separation) determine the characteristic impedance.
|"Twinlead with windows"
||The name says it all: "Twinlead with windows." Sometimes called "railroad track line."
||300 to 450 ohms
|Open wire feed line
||Individual conductors separated by plastic or ceramic spacers placed at intervals.
(One author says "10 to 5,000 ohms.")
||Proprietary open wire feed line formerly manufactured by Gonset Company of Burbank, California, for use as an antenna feed line. Used by some CATV operators for antenna-to-headend transmission.
Local Oscillator. A variable-frequency oscillator built into a radio or television receiver whose output frequency is mixed with the incoming modulated radio-frequency carrier signal to produce the required intermediate frequency. The standard intermediate frequencies in the United States are:
AM Radio receiver: 455 kHz
FM Radio receiver: 10.7 MHz
Analog TV receiver: 41.25 MHz (aural) and 45.75 MHz (visual)
MATV. Master Antenna Television System. A privately-owned television distribution system serving an MDU. In 1940 and 50s, television broadcasting was growing rapidly, but cable television not available. During these years, numerous MDU owners constructed MATV systems to serve their residents. Many MATV systems are quite small – a four-unit apartment building with a rooftop antenna and a Radio Shack amplifier in the attic is an
MATV. An MATV system performs the same function as a CATV/Cable TV system, but with one crucial difference: an MATV does not cross public rights-of-way with any physical medium (copper, glass, or plastic). This may sound like a trivial distinction, but it's vitally important to the parties involved. MATVs do not fall within the legal definition of cable television systems. As such:
They are exempt from local regulation concerning rates, content, level of services, or franchise fees.
They are exempt from most federal regulations applicable to CATV systems.
They are not subject to the must-carry provisions of the 1992 Cable Act (although they are subject to the retransmission consent rules).
Jerrold Electronics Corporation originally started as a manufacturer of distribution amplifiers to serve this market.
MSO. Multiple System Operator; i.e., a company that owns two or more franchised CATV systems.
MDU. Multiple Dwelling Unit: apartment building, condominium building, hospital, retirement home, hospice facility, prison. More generally, this term can be applied to any multiple-building residential facility under common ownership and contained within a single parcel of land, such as apartment or condominium complex, mobile home park, college or university campus, state or national park, military reservation. This term is even applied to non-residential buildings such as office buildings, research laboratories, and similar facilities.
NCE. Non-commercial Educational: a broadcast station (radio or television) specifically licensed by the FCC as a non-commercial station.
NTSC. National Television System Committee, an industry committee created by the FCC for the purpose of selecting a standard format for television transmissions in the United States. Many other countries subsequently adopted the NTSC standard. The NTSC standard is no longer in use for commercial and NCE broadcast stations in the United States and Canada, having been superceded by the digital television standard. Wikipedia.
Pay-TV Descrambler. A freestanding device inserted into the cable between a plain converter and a customer's television set. Most Pay-TV descramblers operate on Channel 3, although Channel 4 descramblers were also available for use in areas with a local broadcast station operating on Channel 3.
A Channel 3 Pay-TV descrambler is connected as follows:
When connected as shown, the descrambler acts on the incoming signal as follows:
If the incoming signal is not scrambled, the descrambler passes it unaltered.
If the incoming signal is scrambled using a compatible scrambling scheme, the descrambler unscrambles it, and passes the unscrambled signal to the TV set.
If the incoming signal is scrambled using a non-compatible scrambling scheme, the result is unpredictable.
Pay-TV descramblers were used during the 1970s and 1980s by cable companies who wished to add a premium channel. As time passed, descrambling converters replaced plain converters, and dedicated Pay-TV descramblers became obsolete.
PL-259 Connector. A 50-ohm coaxial cable connector once used by some CATV equipment manufacturers. This connector was ill-suited for CATV work due to cost and impedance mismatch. This connector was phased out after the introduction of C-Connectors and F-Connectors.
Premium channel; premium signal. This term applies to:
A non-broadcast advertising-free programming channel offered by a cable TV system for a separate line-item charge. Examples: HBO, Showtime, Cinemax, The Movie Channel.
A group of two or more channels, marketed under a common brand name, offered by a cable TV system for a separate line-time charge. Examples: Encore; Starz.
Any channel that offers programming on a per-program basis. Examples: The Movie Channel On Demand.
SPD-30. A 30-dB non-directional loss network manufactured by Jerrold. In a typical application, it is inserted between the output test point of an amplifier and a SLM as shown in the drawing below. The 30-dB insertion loss provides sufficient signal for accurate measurement, but presents a high impedance to the amplifier output circuit to avoid loading the amplifier output stage.
SMATV. Satellite Master Antenna Television System. An MATV system that includes satellite-delivered programing as part of its offerings..
Terminator, termination. A device fitted with a 75-ohm resistive load to terminate a 75-ohm RF signal. In a typical configuration, an F-Connector is used to terminate an unused output port of a splitter or directional coupler.
|Photo: Lew Chandler|
TCI. This term can refer to:
Tele-Communications, Inc., a former MSO based in Denver. TCI was purchased in 1999 by AT&T, whose cable television assets were later acquired by Charter Communications and Comcast Corporation.
Telephone Collectors International, an organization of telephone collectors, hobbyists and historians who are helping to preserve the history of the telecommunications industry through the collection of telephones and telephone-related materials.
Turks and Caicos Islands, a British Overseas Territory consisting of two groups of tropical islands in the Caribbean, Caicos Islands and Turks Islands. Robert B. "Coop" Cooper, a contributor to this website, has written a three-volume memoir about TCI.
Twinlead. Unshielded two-conductor ribbon cable used for the transmission of balanced radio frequency signals. The physical dimensions (conductor diameter and conductor separation) determine the characteristic impedance Z0. The characteristic impedance of virtually all twinlead manufactured for VHF and UHF television signal reception is 300 ohms. Twinlead with stamped open spaces (Fig. 4) is sometimes called "ladder line."
UHF Connector. A rarely-used synonym for PL-259 connector.
Z0. Characteristic impedance.