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 transmission 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.
- 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 feeding multiple customers by means of a cable network. Over the years, as systems began carrying non-broadcast programming, the term became "Cable Television."
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 type of C-Connector 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.
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:
Descrambler.
Drop.
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.
Inside wiring.
IR remote.
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.
MATV. Master Antenna Television System. A privately-owned television distribution system serving an MDU. In late 1940s, television broadcasting was growing rapidly, but cable television not available. During these years, numerous MDU owners constructed MATV systems to serve their residents. Jerrold Electronics Corporation was an early manufacturer of distribution amplifiers to serve this market.
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.
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.
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 |
UHF Connector. A rarely-used synonym for PL-259 connector.
—Neal McLain
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