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 RadioShack Consumer Electronics Glossary: C

Batteries: see C rate.
Electronics: see Capacitor, Capacitance, Collector or Coulomb.
Lighting: see Candela.
Measurement: see centi- (c-).
Weather: see Celsius.
C Rate
Acronym: Capacity Rate
Batteries: The rate of charging or discharging a battery, at room temperature under constant current, expressed as total capacity (1C) divided by the time in hours. For example: 1C indicates that the battery is completely charged or discharged in one hour. 0.2C indicates that the battery is completely charged or discharged in five hours.
Cables: A conductor or a number of conductors packaged together (with or without an insulator material between conductors) that is used to carry an electrical signal.
Video: see CATV.
Cable Run
Audio, Video: The length of cable between an antenna and a receiver.
Metal Detectors: Any type of deliberately concealed treasure, usually consisting of a quantity of money or other valuables.
Electronics, DIY: The adjustment of a measuring device by comparison to an established standard.
Call Forwarding
Telephony: A feature that allows a subscriber to forward an incoming call to another telephone number.
Call Waiting
Telephony: A feature that allows a subscriber to be alerted of another call during a current conversation. Call waiting allows the user to answer the incoming call, but not to connect all parties (connecting all parties is considered a conference call).
Weather: The amount of heat required to raise the temperature of one (1) gram of water one (1) degree Celsius. It is a unit of heat energy.
Acronym: Campus Area Network
Computers, Networking: A computer network that covers a limited geographic area, such as a campus or military base. Compare to HAN, LAN, MAN, WAN.
Lighting: A measurement of light output taken at the source of the light, rather than at the object the light falls onto (as with a foot-candle).
Candle Power: see Candela.
Cannon Connector (Plug): see XLR.
Capacitance (C)
DIY, Electronics: A measurement indicating the ability to store electricity while under load. Capacitance is measured in farads and is always positive.
Capacitive Reactance: see Reactance, Capacitive.
Capacitor (C)
Electronics: A component constructed using two metallic plates separated by a dielectric and used to store electricity while under load. Capacitors are used in a circuit to allow for a variable current while maintaining a constant voltage. When the load is removed, the capacitor will slowly self-discharge. Touching a capacitor with a conductive material before it is fully discharged can cause it to quickly and fully discharge, with the same effect as touching a live wire of comparable power. Large capacitors, such as those used in televisions, store sufficient electricity to cause serious damage, injury and death if they discharge into an item or individual.
Capacitor, Ceramic
Electronics: A capacitor with a dielectric constructed of a ceramic material such as alumina or steatite.
Capacitor, Electrolytic
A polarized capacitor having a very high capacitance-to-volume ratio and consisting of two electrodes in an electrolyte, with a chemical film (the dielectric) on one or both electrodes.
Capacitor, Non-polar(ized)
Electronics: A capacitor that does not have a polarity; that is, there is not a negative or positive lead. Current can flow in either direction.
Capacitor, NPO
Acronym: Negative Positive zerO
Electronics: A polarized capacitor that has both the negative and positive leads at zero.
Capacitor, Polyester
Electronics: A capacitor (either polarized or non-polar) that has a polyester dielectric. Polyester is a resin formed by the reaction between a dibasic acid and a dihydroxy alcohol.
Capacitor, Tantalum
Electronics: A high-capacity capacitor (either polarized or non-polar) that has a tantalum foil anode.
Capacitor, Metal Film
Electronics: A capacitor (either polarized or non-polar) that has a metal film dielectric.
Capacitor, Metal Polypropylene Film
Electronics: A capacitor (either polarized or non-polar) that has a metal polypropylene film dielectric.
Capacitor Microphone: see Microphone, Capacitor.
Capacitor, Trimmer
Electronics: A capacitor having a capacitance that can be modified by the end user; it is used for making fine adjustments.
Capacitor, X7R, Y5P, etc.
Electronics: A Type II capacitor (as opposed to a Type I, or NPO capacitor). The codes indicate the low and high temperature and the maximum change in capacitance from room temperature to high and low temperatures.
X7R Capacitor Ratings Chart
Capacitor, Variable
Electronics: A capacitor having a capacitance that can be modified by the end user.
Batteries: The current in amperes available from a fully charged battery for discharge over a period of time (hours) expressed in ampere-hours (Ah).
Digital Video: A term used in digital imaging to indicate the taking of an image using a digital sensor, rather than a standard camera and film.
Carbon Dioxide (CO2)
Weather: A heavy, colorless gas that is the fourth most abundant constituent of dry air, comprising 0.033% of the total.
Carbon-film Resistor: see Resistor, Carbon-film.
Carbon Microphone: see Microphone, Carbon.
Carbon Resistor: see Resistor, Carbon.
Carbon-zinc Cell
Batteries: A battery consisting of a zinc can anode, a manganese-dioxide cathode, an electrolyte of ammonium chloride and zinc chloride in water. Powdered carbon is added to improve conductivity as well as to hold moisture; the carbon electrode serves to collect electrons from the cathode.
Computers: A sealed package containing memory storage chips or other electronic devices for use in a card slot on a digital camera, printer, computer, or other device.
Cardioid Pattern on a Polar Chart Audio: A unidirectional microphone pickup pattern (or polar pattern) that has the highest sensitivity at 0°, and (ideally) no sensitivity at 180°. It is called "cardioid" because the pattern is shaped like an inverted heart, with "bottom point" of the heart at 0°.

Compare to Omnidirectional, Hyper-cardioid and Ultra-cardioid.

Card Reader
Computers: A device that allows your computer to directly read flash memory cards. See also PCMCIA and PC Card.
Communications, Telephony: The fixed frequency radio signal that carries the communications signal, either through amplitude modulation or frequency modulation.
Electronics: In transistors, either electrons (negative charges) or holes (positive charges), that carry the current.
Carrier, Majority
Electronics: The carrier (electrons or holes) that has a greater density in a transistor.
Carrier, Minority
Electronics: The carrier (electrons or holes) that has a significantly smaller density in a transistor.
Carrier Wave: see CW.
Audio, Turntables: The turntable component that contains the stylus.
Cartridge, Ceramic
Audio, Turntables: A turntable cartridge that provides a high output signal at line-level, at the cost of some signal quality. See What's the difference between a magnetic and a ceramic cartridge? for more details.
Cartridge, Magnetic
Audio, Turntables: A turntable cartridge that provides superior sound, but at a lower signal level. In order to use a magnetic cartridge with a line-level input, you will need to use a pre-amplifier. See What's the difference between a magnetic and a ceramic cartridge? for more details
Cat 1
Acronym: Category 1 cable
Cables: An unshielded twisted-pair cable used for ISDN, telephone connections and doorbell wiring. It is rated at up to 1 MHz and supports up to 1 Mbps. The maximum recommended cable run is 100 meters (328 feet).
Cat 2
Acronym: Category 2 cable
Cables: An unshielded twisted-pair cable used for Token Ring networks. It is rated at 4 MHz and supports up to 4 Mbps. The maximum recommended cable run is 100 meters (328 feet).
Cat 3
Acronym: Category 3 cable
Cables: An unshielded twisted-pair cable used for telephone and networking connections. It is rated at 16 MHz and supports up to 10 Mbps. The maximum recommended cable run is 100 meters (328 feet).
Cat 4
Acronym: Category 4 cable
Cables: An unshielded twisted-pair cable used for 16 Mbps Token Ring networks. It is rated at 20 MHz and supports up to 20 Mbps. The maximum recommended cable run is 100 meters (328 feet).
Cat 5
Acronym: Category 5 cable
Cables: An eight-conductor unshielded twisted-pair cable used primarily for networking and computer connections. It is rated at 100 MHz and supports up to 100 Mbps. Replaced by Cat 5e cable. The maximum recommended cable run is 100 meters (328 feet).
Cat 5e
Acronym: Category 5 enhanced
Cables: An eight-conductor unshielded twisted-pair cable with a plastic rib in the center of the cable to separate the pairs. It is used primarily for networking and computer connections. It is rated at 100 MHz and supports up to 100 Mbps. Replaces Cat 5 cable. The maximum recommended cable run is 100 meters (328 feet).
Cat 6
Acronym: Category 6 cable
Cables: An eight-conductor unshielded twisted-pair cable that differs from Cat-5 in that is uses all four pairs. It is rated up tp 400 MHz and supports up to 400 Mbps.
Cat 7
Acronym: Category 7 cable
Cables: An eight-conductor unshielded twisted-pair cable. It is rated at 600 to 700 MHz and supports up to 600 to 700 Mbps. The maximum recommended cable run is 100 meters (328 feet).
Category 1 Cable: see Cat 1.
Category 2 Cable: see Cat 2.
Category 3 Cable: see Cat 3.
Category 4 Cable: see Cat 4.
Category 5 Cable: see Cat 5.
Category 5e Cable: see Cat 5e.
Category 6 Cable: see Cat 6.
Category 7 Cable: see Cat 7.
Cathode (-) (K)
Batteries: The negatively charged pole of an electrochemical cell.
Electronics: The electrode through which a direct current leaves a component.
DIY: The negative terminal of a semiconductor diode, which is the source of the electrons.
Acronym: Originally Community Antenna Television; now Cable Television
Video: The system of video distribution using direct cable connection to the source, as opposed to wireless broadcast.
Acronym: Citizen's Band
Communications: A public, license-free two-way personal radio service that operates on 40 channels in the 27 MHz band.
Video: The color difference between the blue component and the luma in the Y'Cb'Cr color space. Also called B' - Y, and often abbreviated to Cb (without the apostrophe).
Communications: The frequencies from 3.7 GHz to 7 GHz.
Radar Detectors: A frequency band that extends approximately from 4 GHz to 8 GHz.
Satellite: A frequency band that extends approximately from 3.7 GHz to 4.2 GHz. This term is also used to describe the older (usually 5' to 9' diameter) satellite antennas, that operate on these frequencies.
Acronym: Constant Bit Rate
Audio: An encoding method in which the bit rate remains the same throughout the audio file. See VBR.
Acronym: Charge-Coupled Device
Digital Video: An image sensor that reads the charges from the sensor's photosites one row at a time.
CCD Raw Format: see RAW.
Acronym: Closed Circuit TeleVision
Digital Video, Security: A television system contained within a certain area.
Acronym: Compact Disc
Audio, Computers: An optical media format that can hold to 74 minutes of high definition audio or 650 MB of data. See also SACD.
CD Burner
Computers: Hardware that writes to a CD-R either audio (up to 74 minutes) that you can play in a standard CD player or data (up to 650 MB).
CD Ripper
Audio: Software that reads the audio information from an audio CD and then records the data to a file on your computer.
CD Text
Audio: The disc and track information embedded on an audio CD.
Acronym: Compact Disc-Recordable
Computers: A type of compact disc that can be used to record digital information. A CD-R can be used to store computer files or digital audio. Like all digital media, the copy made on the CD-R is identical to the original. A CD-R can be recorded upon only once -- it cannot be erased or re-recorded over.
Acronym: Compact Disc-Read Only Memory
Computers: A CD-ROM is a standard compact disc containing data files that may include text files, audio files, video files or any other type of files. Most CD-ROM's can hold 650 MB of data. CD-ROM's can only be read using a PC with a CD-ROM drive.
Acronym: Compact Disc-Rewritable
Computers: A CD-RW is just like a CD-R except that it can be written over or re-recorded over. Like CD-R, the CD-RW is in digital format, and therefore allows identical copying of files with no loss of quality. These discs can record and erase audio and data up to 1,000 times.
CDA (.cda)
Acronym: CD Audio
Audio: CDA is a method of displaying audio tracks, much like a menu, used by standard audio CD's.
Acronym: Compact Disc DataBase
Audio: The CDDB is a commercial on-line lookup tool for retrieving album, artist, and track information, such as for completing MP3 ID3 tags or accessing information on pre-recorded CD's.
Acronym: Code Division Multiple Access
Telephony: A second-generation (2G) cellular system in which each voice circuit is labeled with a unique code and transmitted on a single channel simultaneously along with many other coded voice circuits. CDMA telephones are available in 800 or 1900 MHz versions. The fundamentals of code division technology were originally developed by Claude Shannon and Robert Pierce in 1949.
CDMA is also called IS-95, IS-95-A, and IS-95-B. The IS-95-A revision to the original IS-95 standard occurred in 1995. The IS-95B revision merged the IS-95-A standard with the PCS standard (ANSI J-STD-008) and the Rate Set 2 standard (TSB74).
Acronym: Code Division Multiple Access, 1 times (x) Evolution - Data Only
Telephony: see CDMA, HDR.
Acronym: Code Division Multiple Access, 1 times (x) Radio Transmission Technology 
Telephony: A cellular system using one times radio transmission technology with 1.25 MHz channels. 1xRTT CDMA supports peak data speeds up to 144 Kbps (kilobits per second), with average speeds of 50 to 70 kbps, and up to a doubling of voice capacity. Also called 3G 1x.
Acronym: Code Division Multiple Access (for the year) 2000
Telephony: The United States' proposal for third-generation (3G) CDMA technology in order to double CDMA system capacity and improve data rates to 144 Kbps (kilobits per second). Also called IS-95-C.
Acronym: Code Division Multiple Access, High Data Rate
Telephony: A packet data cellular solution that focuses on providing support for data rather than for voice. Peak speeds are 2.2 Mbps (Megabits per second), with each user in a loaded network expected to see speeds around 800 Mbps. Also called CDMA, 1xEv-DO (1 times (x) Evolution - Data Only).
Acronym: Code Division Multiple Access One
Telephony: A narrowband, second-generation (2G) digital wireless technology developed by Qualcomm.
Acronym: Cellular Digital Packet Data
Telephony: Cellular technology that allows data files to be broken into a number of packets and sent along idle channels of existing cellular voice networks. Transmission rates are limited to 19.2 kbps.
Acronym: Conformité Européenne
The organization responsible for setting product safety standards in the European Union. The CE mark is found on the same types of products as the UL mark (United States) and the CSA mark (Canada).
Weather: The lowest cloud layer that is reported as broken or overcast. If the sky is totally obscured, then it is the height of the vertical visibility.
Batteries: A single unit designed and used to produce an electrical DC voltage through an internal electrochemical reaction.
Telephony: 1) The coverage area in a cellular system resulting from operation of a single, multiple-channel set of base station frequencies.
2) The base station equipment servicing a coverage area.
Cell, Dry
Batteries: An electrochemical cell that uses a non-liquid electrolyte (usually a paste).
Cell, Primary
Batteries: An electrochemical cell that cannot be recharged once it is discharged.
Cell, Secondary
Batteries: An electrochemical cell used to store electricity, so that once discharged, it can be recharged by putting current through the cell in the opposite direction from the discharge current.
Cell, Voltaic
Batteries: A primary cell having two unlike electrodes immersed in a solution that chemically interacts to produce a voltage.
Cellular Digital Packet Data: see CDPD.
Cellular, Fixed
Telephony: A cellular network that is set up to support fixed rather than mobile subscribers. Also called Fixed Wireless.
Cellular Geographic Serving Area: see CGSA.
Cellular Telephone
Telephony: A wireless telephone system that uses the cellular technology developed by Bell Laboratories. Also called CMRT (Cellular Mobile Radio Telephone, Mobile Telephone or Cell Telephone.
Cell, Wet
Batteries: A secondary cell that uses a liquid electrolyte.
Celsius (C)
Weather: A temperature scale where water at sea level has a freezing point of 0°C (Celsius) and a boiling point of +100°C. More commonly used in areas that observe the metric system of measurement. Created by Anders Celsius in 1742. In 1948, the Ninth General Conference on Weights and Measures replaced "degree Centigrade" with "degree Celsius."
Electronics: A connection that is made at the midpoint between the two ends of a transformer's winding.
Center-tapped Rectifier: see Rectifier, Center-tapped.
Center-tapped Transformer: see Transformer, Center-tapped.
Center Weighted
Digital Video: An autoexposure system that uses the center portion of the image to adjust the overall exposure value. See Spot Metering and Matrix metering.
centi- (c-)
Measurement: SI / Metric unit of decimal measurement, equal to 10-2 or 0.01.
Measurement: An SI (metric) unit of measurement equal to .39 inches or 1/100th of a meter.
Acronym: Central Office Exchange Service
Telephony: A service providing similar benefits and capabilities as a PBX (Private Branch Exchange) in which a telephone company allows its facilities to be used by subscribing businesses, rather than each business providing and maintaining its own facilities.
Ceramic Capacitor: see Capacitor, Ceramic.
CF: see CompactFlash™.
Acronym: Centimeter-Gram-Second
Measurement: An early system of physical units of measurement that predates and has been largely incorporated into or replaced by* the SI (or metric) system. It is now predominantly used only by physicists.
Property Basic Unit Calculated or Equivalent Value
Length meter  
Mass gram  
Time second  
Capacitance cm 1.113*10-12 farad
Charge* esu
√ (g * cm3 sec-2)
3.336*10-10 coulombs
Electric field* statvolt/cm
Electric potential* statvolt erg/esu
299.8 volts
Energy erg dyne * cm
Force dyne g * cm * sec-2
Inductance* sec2/cm sec2/cm = 8.988*1011 henry
Magnetic field gauss oersted
Magnetic flux gauss * cm2 gauss * cm2
Physical Resistance sec/cm sec/cm
Physical Resistivity sec sec
Power erg/sec erg/sec
Pressure* bayre 0.1 pascal
Acronym: Cellular Geographic Serving Area
Telephony: A geographic cellular coverage region defined by the FCC. The two types are Metropolitan Statistical Areas (MSA's) and Rural Statistical Areas (RSA's).
Audio: An audio signal sent to a speaker. Used to describe the quality of sound by the number of individual outputs. For example, a stereo system with separate left and right speaker outputs provides two-channel sound.
Communications: A memory location used in scanners or two-way radios to store a single frequency.
Electronics: The semiconductor path through which current flows in an FET (Field Effect Transistor).
Video: A specific video broadcast transmit frequency (such as Channel 3).
Batteries: To recharge a secondary battery.
DIY, Electronics: A quantity of electrical energy. The symbol for this is Q.
Charge Current: see Current, Charge.
Charge Rate
Batteries: The current at which a secondary battery is charged.
Electronics: An inductor used to oppose the flow of alternating current and pass the flow of direct current.
Choke, RF
Acronym: Radio Frequency Choke
Electronics: A choke designed to remove unwanted frequencies from a cable.
Chroma: see Chrominance.
Chromatic Aberration
Digital Video: A fringing effect around the edges of an object in a digital image, caused by the lens not focusing correctly.
Video: The color component in a composite video signal. More properly called Chroma.
GPS, Measurement: An instrument that keeps very accurate time and is particularly used in navigation.
Acronym: Camera Image File Format
Digital Video: A file format used by many camera makers for storing digital images.
Communications, Telephony: A connection between two users; used synonymously with Channel.
DIY, Electronics: An interconnection of electronic components to provide an electrical path between the positive and negative terminals of a power source.
Circuit Breaker
DIY, Electronics: A device used to protect a circuit by opening or breaking the circuit when the current exceeds a maximum value.
Circuit Breaker Panel
DIY, Electronics, Plug 'n Power: An electric panel that contains the circuit breakers of a building.
Circuit, Class #
Electronics: Wired power circuits are rated as a particular class as set down in Article 725 of the NEC (National Electrical Code). There are three circuit classes:
Class 1 Circuit
The portion of the wiring system between the load side of the overcurrent device or power-limited supply and the connected equipment. The voltage and power limitations of the source are in accordance with NEC Section 725-21. Regardless of whether the voltage is line voltage or low voltage, a Class 1 circuit must be treated as a line voltage circuit and be run in a conduit.
Class 2 Circuit
The portion of the wiring system between the load side of a Class 2 power source and the connected equipment. A Class 2 power source is limited to the following ratings:
Voltage Wattage Current
0 to 20 volts 100 watts 5 amps
21 to 30 volts 100 watts 3.3 amps
31 to 150 volts 0.5 watts 5 milliamps
Note: As the voltage increases, the power limit is decreased.
In addition to the power limitation, a Class 2 circuit must remain separated from line voltage conductors. Unlike a Class 1 circuit, it can be installed without a conduit.
Class 3 Circuit
The portion of the wiring system between the load side of a Class 3 power source and the connected equipment. A Class 3 power source is inherently limited to between 31 and 100 volts at 100 watts, and non-inherently limited to between 31 and 150 volts at 100 watts. Like a Class 2 circuit, it can be installed without a conduit; ;however, because has higher voltage and power limits than a Class 2 circuit, the NEC has additional requirements for safety.
Circuit Diagram
Electronics: A system diagram that illustrates the specific operation of all components. Compare to a Block Diagram, which illustrates the general operation and interaction of the primary element groups using blocks to represent each group.
Circuit, Open
DIY: An electrical circuit where there is no electric current flowing, as the circuit is incomplete. This can be caused by a blown fuse.
Circuit-switched Network
Telephony, Computers: A communications system that uses a dedicated circuit for each individual transmission or telephone call. Circuit-switched networks are faster but less efficient than packet-switched networks.
Weather: Clouds composed of small particles, mostly ice crystals. Because the particles are fairly widely dispersed, this usually results in relative transparency and whiteness, often producing a halo phenomena not observed in other clouds forms. These clouds generally have bases above 20,000 feet in the mid-latitudes, and are classified as high clouds. They include all varieties of cirrus, cirrocumulus, and cirrostratus clouds.
Weather: A cirriform cloud with vertical development, appearing as a thin sheet of small white puffs which give it a rippled effect. It often creates what is called a "mackerel sky", since the ripples may look like fish scales. Sometimes it is confused with altocumulus, however, it has smaller individual masses and does not cast a shadow on other elements. It is also the least common cloud type, often forming from cirrus or cirrostratus, with which it is associated in the sky.
Weather: A cirriform cloud that develops from cirrus spreading out into a thin layer, creating a flat sheetlike appearance. It can give the sky a slightly milky or veiled look. When viewed from the surface of the earth, these ice crystals can create a halo effect around the sun or moon. This cloud is a good precursor of precipitation, indicating it may occur within 12 to 24 hours.
Weather: One of the three basic cloud forms (the others are cumulus and stratus). It is also one of the three high cloud types. Cirrus are thin, wispy clouds composed of ice crystals and often appear as veil patches or strands. In the mid-latitudes, cloud bases are usually found between 20,000 to 30,000 feet, and it is the highest cloud that forms in the sky, except for the tops, or anvils, of cumulonimbus, which occasionally build to excessive heights.
Metal Detectors: American coins that are still in circulation, usually dating from 1965 and on, so called because they consist of one metal clad onto a baser metal.
Class # Circuit: see Circuit, Class #.
Class # Transformer: see Transformer, Class #.
Weather: the state of the sky when no clouds or obscurations are observed or detected from the point of observation.
Audio: An audio distortion effect caused when an amplifier attempts to output a voltage (or current) level beyond the capabilities of the power supply. The name is derived from the appearance of the waveform, in which the top and bottom are flat ("clipped off") rather than curved.
Clock, Atomic
GPS: A very precise clock that operates using the elements cesium or rubidium. A cesium clock has an error of one second per million years. GPS satellites contain multiple cesium and rubidium clocks.
Clock Rate
Electronics: The oscillating frequency of the primary oscillator in a system.
Close Focus
Binoculars: The closest distance at which the binoculars can focus on the target.
Audio: Cloth describes a type of cone that is made out of woven fibers bonded with a resin or plastic. A cloth cone has a much higher stiffness and provides an extended frequency response. One type of cloth cone is made out of Kevlar®.
Weather: a visible collection of minute particle matter, such as water droplets and/or ice crystals, in the free air. A cloud forms in the atmosphere as a result of condensation of water vapor. Condensation nuclei, such as in smoke or dust particles, form a surface upon which water vapor can condense.
Cloud Bank
Weather: a well-defined cloud mass that can be observed at a distance. It covers the horizon, but is not directly overhead.
Cloud, Wall
Weather: An abrupt lowering of a cloud from its parent cloud base, a cumulonimbus or supercell, with no visible precipitation underneath. Forming in the area of a thunderstorm updraft, or inflow area, it exhibits rapid upward movement and cyclonic rotation. It often develops before strong or violent tornadoes.
Clouds, High
Weather: A term used to signify cirriform clouds that are composed of ice crystals and generally have bases above 20,000 feet. The main types of high clouds are cirrus,cirrocumulus, and cirrostratus. This altitude applies to the temperate zone. In the polar regions, these clouds may be found at lower altitudes. In the tropics, the defining altitudes for cloud types are generally higher.
Clouds, Low
Weather: a term used to signify clouds with bases below 6,000 feet and are of a stratiform or a cumuliform variety. Stratiform clouds include stratus and stratocumulus. Cumuliform clouds include cumulus and cumulonimbus. This altitude applies to the temperate zone. In the polar regions, these clouds may be found at lower altitudes. In the tropics, the defining altitudes for cloud types are generally higher.
Clouds, Middle
Weather: A term used to signify clouds with bases between 6,000 and 18,000 feet. At the higher altitudes, they may also have some ice crystals, but they are composed mainly of water droplets. Altocumulus, altostratus, and nimbostratus are the main types of middle clouds. This altitude applies to the temperate zone. In the polar regions, these clouds may be found at lower altitudes. In the tropics, the defining altitudes for cloud types are generally higher.
Acronym: Current Mode Logic
Electronics: see ECL.
Acronym: Complementary Metal-Oxide Semiconductor
Digital Video: An imaging system used by digital cameras.
Electronics: A logic device that uses enhancement-mode MOSFET's instead of transistors.
Acronym: Commercial Mobile Radio Service
Telephony: The classification used by the FCC to cover all commercial wireless service providers, including Personal Communications Services, cellular, and Enhanced Specialized Mobile Radio.
Acronym: Cellular Mobile Radio Telephone
Telephony: The original, first-generation (1G) mobile telephone technology. Technically, only systems based on this technology, such as AMPS, are cellular systems. However, the term is often applied to any mobile telephone system.
Coax, Coaxial
Cables: A cable with one inner conductor, and an outer shield insulated from one another by a dielectric foam, used mostly in CATV, and 10Base2 Ethernet.
Code Block
Communications, Scanners: A group of consecutive ID codes used in trunked system fleet maps that can be any size (up to all 250).
Acronym: Compression / decompression
Digital Audio, Digital Video: A system for compression and decompression of digital files.
DIY, Electronics: A component created by winding multiple turns of wire around a cylindrical form or onto a metal core.
Metal Detectors: see Search Coil.
Coil, Elliptical
Metal Detectors: A search coil with an ellipse shape. This coil can be either concentric or wide scan type.
Coil, Search
Metal Detectors: A circular (or other shaped) plastic housing containing single or multiple transmit and receive windings in a specific orientation or configuration to emit and receive signals from ground and targets. Also called Search Loop, Coil or Se arch Head.
Coin Depth Indicator
Metal Detectors: A visual indicator, used in conjunction with calibrated circuitry, to show the depth of buried coins.
Collector (C)
Electronics: The semiconductor region in a bipolar junction (NPN or PNP) transistor through which a flow of charge carriers leaves the base region.
Color Balance
Digital Video: The accuracy with which the colors in an digital image match those in the original scene.
Color Correction
Digital Video: The process of correcting or enhancing the color of a digital image.
Color Depth
Digital Video: The number of bits assigned to each pixel in an image and the number of colors that can be created from those bits. True Color uses 24 bits per pixel to render 16 million colors.
Color-Filter Array
Digital Video: The filter dyes that are placed directly over each pixel on the chip surface of a digital image sensor (See CCD, CMOS).
Color Space
Video: The mathematical representation of a color system, such as RGB or Y'Cb'Cr.
Plug 'n Power: A signal that is sent from a transmitter to a receiver and triggers an event such as ON or OFF, Bright or Dim. 
Commercial Advance
Video: A feature in some VCR's that marks commercials after recording and automatically fast-forwards through them during replay of the recording.
Commercial Mobile Radio Service: see CMRS.
Compact Disc: see CD.
Compact Disc Database: see CDDB™.
Compact Disc-Read Only Memory: see CD-ROM.
Compact Disc-Recordable: see CD-R.
Compact Disc-Rewritable: see CD-RW.
CompactFlash™ (CF)
MP3, Digital Video: There are three types of CompactFlash™ cards:
CF Type I: 5mm high
CF Type II: 9mm high
CF Type III: double-height
Type I devices are all solid-state but Type II devices include the new Microdrive™ by IBM, a miniature rotating hard drive. CompactFlash is the most common type of digital camera flash memory storage.
GPS: A navigational instrument for measuring direction. A magnetic needle is freely suspended so that it will move according to the earth's magnetic field, and will align itself with the magnetic north and south poles.
DIY, Electronics: An electronic or electrical element in a circuit.
Video: An element of a video signal, such as the Y component of the Y'Cb'Cr color space.
Component, Active
Electronics: A component that changes the signal between input and output. Transistors are active components.
Component, Passive
Electronics: A component that does not amplify a signal. Resistors and capacitors are passive components.
Component Video
Video: A video system that retains the original color elements separately rather than combining them into a single signal (as with composite video). This creates a signal with a higher color bandwidth than that of composite video. Component video cables have three RCA plugs on each end. The color elements are Y, Cb, and Cr for standard component video, and Y, Pb, and Pr for high-definition component video.
COM port
Computers: A serial communication port that supports the RS-232 standard of communication.
Composite Video
Video: A video signal that consists of two elements: a black-and-white signal (luminance or luma) and a color signal (chrominance or chroma). Composite video can be either analog or digital.
Computers: The process of reducing the size of a file. Compression is either lossless or lossy.
MP3 Audio: MP3 files are generally compressed at a ratio of 12:1.
Metal Detectors: A search coil configuration using one or more transmit windings, and one receive winding, each having unequal diameters aligned on a common center. When arranged on the same plane, this is called coplanar concentric.
Electronics: The original name for a capacitor.
Condenser Microphone: see Microphone, Capacitor.
Conduct, Conductive, Conductivity
Electronics: To carry an electrical current or signal. A material which conducts electricity is said to be conductive. The property of a material to conduct electricity is called conductivity.
Metal Detectors: Conductivity is the measure of a metal target's ability to allow eddy currents to generate on its surface.
Conductive Salts
Metal Detectors: One of the major mineral types which make up the positive ground matrix. Wet, ocean-salt sand produces a positive rise or metallic type response on an air tuned threshold.
Electronics: An expression of conductivity equal to the ratio of the current passing through a conductor to the potential difference between the two ends of that conductor.
DIY, Electronics: An electrical path that offers relatively little resistance.
Cables: The wire or combination of wires that carries the electrical current or signal.
Conductor, Solid
Electronics, Cables: A conductor that is composed of a single solid wire. Solid conductors have less signal loss and higher conductance than stranded conductors, but are less flexible. Solid conductors are described by their diameter, expressed as the wire's gauge, as in a 16 gauge conductor.
Conductor, Stranded
Cables, Electronics: A conductor that is composed of smaller strands of wire twisted together. Stranded conductors are more flexible than solid conductors, but have greater signal loss and less conductance. Stranded conductors are described by the number of strands and their individual diameters, such as a 7 x 32 conductor, which would be 7 strands of 32 gauge wire twisted together.
Electrical: A pipe (generally either metal or plastic) that is used to protect electrical wires.
Audio: The cone-shaped part of a speaker driver that moves the air, producing sound waves.
Cone Material
Audio: What is used to construct the actual cone. Different materials allow for different advantages and disadvantages. Cone materials commonly found in RadioShack speakers are paper, cloth, polypropylene and Kevlar®.
Constant Bit Rate: see CBR.
Constellation, Satellite
GPS, Satellite: The arrangement in space of a set of satellites.
Electronics: The part of a switch, relay or connector that carries the current.
Electronics: A relay used to switch heavy current at high voltage.
Cables, Electronics: A term describing a circuit or conductor that provides a complete electrical path, allowing a steady signal.
Continuous Autofocus
Digital Video: An autofocus system that is always on.
Video: A measure of the rate of change in the brightness in an image. A high-contrast image is in simple black and white; a low-contrast image consists of very close shades of gray.
Control Box
Metal Detectors: A metal or plastic box which holds the circuit boards, indicators, meter, controls and power supply.
Plug 'n Power: A remote device (transmitter) that is used to send X-10 signals to a module (receiver). Controllers can be plugged into an electrical outlet or wired into the electrical system. Most have push-buttons, but some are timers, motion-sensors or wireless remotes.
Control Station
Communications: A mobile transceiver at a stationary location such as at an office or a construction site.
Conventional Scanning
Communications: Also called Standard Scanning. See Scanning, Conventional.
Computers: A software program that transforms one file format to another.
Electronics: A device transforms one voltage to another or one plug type to another. Also called Adapters. The types of converters are: AC to AC (Travel, or Foreign Voltage, Conveters or Adapters), AC to DC (AC Converters or Adapters), DC to AC (Inverters), and DC to DC (Car, or 12-volt, Converters or Adapters).
Metal Detectors: A metal detector configuration allowing versatility in operator handling by allowing more than one operation method ( i.e., hand held and body mount). Also called Combination.
Metal Detectors: Any search coil configuration in which transmit and receive windings occupy the same level or plane.
Audio, Video, Computer, Software: The right of the creator of an original work, such as recorded music, television shows, movies, and audio books, to protect that work from unauthorized copying.
Coulomb (C)
DIY, Electronics: A measurement of electricity indicating the amount of electricity that is transferred by 1 ampere in one second.
Audio, Turntables: The large section at the rear of the tonearm, used as a balance to counter the weight of the front of the tonearm.
Acronym: Central Processing Unit
Computers: The central processor of a computer system, containing main storage, arithmetic unit, registers, etc.
Video: The color difference between the red component and the luma in the Y'Cb'Cr color space. Also called R' - Y, and often abbreviated to Cr (without the apostrophe).
Audio: A device that accepts an audio input and divides it into two or more frequency bands so that a speaker driver does not receive frequencies outside of its range.
Crossover, Active (Electronic Crossover)
Audio: A crossover comprised of solid state electronics and located between the audio source and the amplifier so that it divides the audio input before it is amplified.
Crossover Cable
Cables: A cable that connects two identical ports (parallel, USB, etc.) and crosses the transmit and receive pins so that two devices can communicate directly without the use of a hub or other intermediate device.
Crossover Frequency: see Frequency, Crossover.
Crossover, Passive
Audio: A crossover comprised of inductors, capacitors, or other passive components and located between the amplifier and the speaker drivers so that it divides the audio input after it is amplified.
Electronics, Communications: An unintentional and unwanted signal in a circuit or channel caused by a signal transmitted on a different circuit or channel.
Acronym: Cathode Ray Tube
Computers: A device that uses electrons to form patterns onto a viewing screen under the direction of magnetic fields to form patterns. Used as a synonym for visual display screen.
Electronics: A semiconductor, either man-made or naturally-occurring (such as galena and iron pyrite) that acts as a diode. Early radios and scanners required specific crystals to receive specific frequencies.
Crystal Controlled Oscillator
Metal Detectors: A transmit oscillator which uses a crystal to maintain a stable output frequency.
Acronym: Canadian Standards Association
The organization responsible for setting product safety standards in Canada. The CSA mark is found on the same types of products as the UL mark (United States) and the CE mark (European Union).
Acronym: Cellular Telecommunications and Internet Association (originally Cellular Telecommunications and Industry Association)
Telephony: An international organization representing the wireless communication industry.
Cue, Cueing
Audio, Turntables: A mechanism to lift and lower the tonearm. "Damped" cueing indicates that the mechanism includes a method (mechanical, pneumatic or hydraulic) to slow the rate of descent to avoid damage to the record or the stylus.
Weather: clouds composed of water droplets that exhibit vertical development. The density of the droplets often blocks sunlight, casting shadows on the earth's surface. With increasing vertical height, they are often associated with convection. Bases of these clouds are generally no more than 3,000 feet above the ground, but they can develop past the troposphere in both temperate and tropical latitudes. They are classified as low clouds and include all varieties of cumulus and cumulonimbus. The opposite in type are the horizontal development of stratiform clouds.
Weather: a vertically developed cumulus cloud, often capped by an anvil-shaped cirriform cloud. Also called a thunderstorm cloud, it is frequently accompanied by heavy showers, lightning, thunder, and sometimes hail, tornadoes or strong, gusty winds.
Cumulonimbus Mammatus
Weather: a portion of a cumulonimbus cloud that appears as a pouch or udder on the under surface of the cloud. Although they do not cause severe weather, they often accompany storms. They may slowly vary in size, since they are an area of negative buoyancy convection, and is associated with severe turbulence in the lower sections of the cloud. Related terms: mammatocumulus
Weather: one of the three basic cloud forms (the others are cirrus and stratus). It is also one of the two low cloud types. A cloud that develops in a vertical direction from the base (bottom) up. They have flat bases and dome- or cauliflower-shaped upper surfaces. The base of the cloud is often no more than 3,000 feet above the ground, but the top often varies in height. Small, separate cumulus are associated with fair weather (cumulus humilis). With additional heating from the earth's surface, they can grow vertically throughout the day. The top of such a cloud can easily reach 20,000 or more into the troposphere. Under certain atmospheric conditions, these clouds can develop into larger clouds, known as towering cumulus (cumulus congestus), and may produce a rain shower. Further development may create a cumulonimbus.
Cumulus Congestus
Weather: a strongly sprouting cumulus cloud with generally sharp outlines and often with great vertical development. It may occur as tower-like clouds with cauliflower tops. These clouds may produce abundant showers and may develop further into cumulonimbus. Related term: towering cumulus
Cumulus Fractus
Weather: cumulus clouds that appear in irregular fragments, as if they had been shred or torn. Also appears in stratus clouds (called stratus fractus), but not in cirrus clouds.
Cumulus Humilis
Weather: cumulus clouds with little or no vertical development characterized by a generally flat appearance. Their growth is usually limited by a temperature inversion, which is marked by the unusually uniform height of the clouds. Also called fair-weather cumulus.
Cumulus Mediocris
Weather: Cumulus clouds characterized by moderate vertical development with upper protuberances not very marked in appearance. This cloud does not produce precipitation, but could develop into towering cumulus or cumulonimbus which do.
Cumulus, Towering
Weather: Another name for cumulus congestus, it is a rapidly growing cumulus or an individual dome-shaped clouds whose height exceeds its width. Its distinctive cauliflower top often mean showers below, but lacking the characteristic anvil of a cumulonimbus, it is not a thunderstorm.
Current (I)
DIY, Electronics: The flow of electricity, measured in amps, that results from applying one volt to a circuit with a one ohm resistance. Alternating current flows back and forth and is also measured in hertz (the number of cycles per second). Direct current typically flows from negative to positive.
Weather: A horizontal movement of water, such as the gulf stream off the east coast of north america, or air, such as the jet stream.
Current, Charge
Electronics, Battery: The current that flows to charge a capacitor or battery when voltage is applied.
Current, Eddy
Metal Detectors: Small circulating currents produced on the surface of metal by the transmitted electromagnetic field. These currents then produce a secondary electromagnetic field which is then detected by the search coil receiver windings, resulting in inductive imbalance between the windings.
Current, Forward
Electronics: The current in a semiconductor that results from conduction by majority carriers across the p-n junction.
Current Mode Logic: see ECL.
Current, Reverse
Electronics: The current in a semiconductor when the junction is reverse biased.
Acronym: Continuous Wave
Communications: A method of carrier wave modulation used for sending Morse code.
Batteries: One sequence of charging and discharging a battery.
Electronics: The period in which a repeating waveform moves from zero to a positive maximum, then through zero again to a negative maximum and then back to zero, as shown below. The dashed line represents the zero position.
Elements of a waveform
Weather: An area of closed pressure circulation with rotating and converging winds, the center of which is a relative pressure minimum. The circulation is counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. Also called a low pressure system and the term used for a tropical cyclone in the Indian Ocean. Other phenomena with cyclonic flow may be referred to by this term, such as dust devils, tornadoes, and tropical and extratropical systems. The opposite of an anticyclone or a high pressure system.

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