C-band
A 4 GHz signal
frequency. It is used by satellites for broadcasting
prerecorded network programming and popular cable services
for satellite dish reception. This is opposite the use of
the Ku-band. C-band is measured in degrees Kelvin and Ku
band is measured in decibels. The lower the measurement in
decibels or Kelvin, the better the picture. C-band
broadcasts 12 channels on vertical polarity and 12 channels
on horizontal polarity totaling 24 channels.
C-Bus
A cluster, inside a (RISC) processor uses this "private bus"
for direct DRAM and the IC connections.
Cables and
connectors
The electricity-handling properties of cables determine
their function: (1), data and/or voice impedance; (2),
attenuation, and grounding capacitance; (3), stranded or
solid wire; (4), shielding materials may be either foil tape
or braided; (5), shielding of individual wires, pairs of
wires, groups of wires, overall, and not at all.
Computer communications cables should also be certified by Underwriters Laboratories, Inc. (UL) and CSA listed, and depending on application, "acceptable" to OSHA and/or passing the VW-1 Vertical Flame Test. Cable shielding must meet FCC regulations.
When ordering cable, determine your maximum requirements for the cable&emdash;how much power it may carry, the length of the longest cable, how much shielding it may need, the physical environment where it will be laid, and cable function. Work with your cable source's sales person to insure that the selected cable will meet your requirements.
Other references: Instrument and Communications Cable, Computer Cable, Plenum Cable, IBM -standard cables, and EIA/TIA Category Standard unshielded twisted-pair (UTP) cables.
Note: PC What's The Problem? includes identification, test, repair and replacement suggestions.
Cable Bandwidth
A cable specification. The difference, expressed in Hertz (Hz), between the lowest and highest frequencies of a transmission channel. (Leased phone lines handle multiple channels.)
CAM
Content-Addressable Memory is combined with a control structure to perform associative processing which manipulates data based on matching, or associating, an input value with other values stored in an array. Because each memory location has this computational capability, the entire memory array can be examined at the same time. (CAMs can even be set to store associated data in other available RAM if the total number of associative and associated bits exceeds the width of the CAM.)
CAMs are used for data-filter and data-translator applications including real-time list searches and entry maintenance. Data-filter capabilities can be used in network bridges, routers, and firewall server systems. Data-translator capabilities can be used in switches (for header translation), caches (for main storage to cache location translation), and compression (for symbol translations).
Capacitor
An electrical component that has two closely-spaced metal plates X and Y, insulated from each other and can store an electrical charge in the insulated space between them. When an electrical charge is applied to both the X and Y plates, one plate has a surplus of electrons, the other a shortage. An electrostatic stress arises within the insulation separating the two plates. Depending on the capacity of the insulation material used, a charge is stored. This capacity is known as capacitance and is measured in farads: F.
There are two basic types of capacitors; polarized (which must be properly aligned when placed in a circuit) and non-polarized capacitors (which can be placed in a circuit with either contact oriented to the circuit).
Polarized capacitors are clearly labeled; placing one in a circuit backward would destroy it and damage the circuit. (They can also be damaged if the circuit exceeds the capacitor's working-voltage (WV) rating.) Polarized capacitors have values generally of 1µF or above.
Aluminum-electrolytic-type capacitors have a value range between 0.068µF to 200kµF and a tolerance between -10% and +75%. These capacitors are used for power-supply filtering and bypass coupling.
Tantalum-electrolytic-type capacitors have a value range between .001µF to 1kµF and a tolerance between 5% and +20%. These capacitors are very stable and have a very long life. They are used for bypass circuits; coupling and decoupling circuits.
Non-polarized capacitors have values generally of 1µF or less. Ceramic-type capacitors have a value range between 1pF to 2.2µF and a tolerance between 5% and 30%. These capacitors are used for transient decoupling and for bypass circuitry. Their values change to match the electrical frequency but can also be effected by temperature. Non-polarized capacitors can be damage if the circuit exceeds the capacitor's WV rating.
Ceramic Disc-type capacitors. Use low-K capacitor for high frequency (HF) coupling, tuned mica circuits, for filtering out electrical noise up to 500 MHz. Use high-K capacitor for RF coupling, decoupling, temperature compensation and for use where capacitance stability is not critical. While a Ceramic Disc capacitor may be replaced with a Polystyrene capacitor (with the same parameters), its leads must be similar in length and diameter to the original particularly for use in RF circuits.
Mica-type capacitors have a value range between 1pF to 1µF and a tolerance between 1% and 30%. These very stable capacitors are used in circuits provide precision timing functions and may be used with RF-circuits and oscillators.
Paper capacitors provide acceptable suppression of transient electrical noise and are stable enough for general purposes. However, because they can absorb moisture, they should only be used in controlled low-humidity environments.
Polycarbonate-type capacitors are used in high frequency (HF) coupling and decoupling. They have near-linear capacitance which is temperature sensitive. For many implementations, a replacement can have a higher voltage rating.
Polypropylene-type capacitors have a value range between 1pF to 10µF and a tolerance between 2% and 10%. These capacitors are very sensitive and particularly good for timing circuits, high fidelity circuits, and those designed for filtering out electrical noise.
Polystyrene-type capacitors have a value range between 51pF to 0.15µF and a tolerance between 1% and 5%. Because there is little change in capacitance due to temperature changes, they are used for audio circuits and provide sufficient stability for timing, tuning and oscillator circuits.
Polyester and mylar-type capacitors have a value range between .001pF to 10µF and a tolerance between 5% and 20%. Like those made with polypropylene, capacitors made with these insulators provide good filtering and suppression of transient electrical noise. Capacitors of this type are good for audio applications that require small size and low power.
Some capacitors use paper as an insulator. These capacitors are low in cost and in weight. A polycarbonate-type capacitor, with capacitance and voltage ratings matching the original, may be used as a replacement. Safety "cap" capacitors may be found in high-voltage circuits; such as, a monitor(or TV). This type of hold-down capacitor has two pairs of legs, each one an internal jumper connected to one side of the cap. The capacitor sits between the flyback/IHVT (integrated high voltage transformer) and the H.O.T (horizontal output transistor). If removed, the monitor will not work.
Capattery is a capacitor with a capacitance value high enough to replace a battery.
Note: PC What's The Problem includes identification, test, repair and replacement suggestions.
Carbon-Composition (CC) resistors
These are referenced with all others as: Resistors.
Category 1 Cable
It supports public telephone services including low-speed data transmissions.
Category 2 Cable
It supports 1.54 Mbps ISDN and T1/E1 services.
Category 3 Cable
This EIA/568 specification supports transmissions up to 16 MHz for data and voice networks including: 4-Mbps Token Ring, IEEE 802.3 Ethernet, 10-Mbps 10Base-T, 100-Mbps 100Base-T4 , and most telephone, minicomputer and mainframe data rates.
Specifications: capacitance is 18 pF, impedance is 100 ± 15 ohms. At 1 MHz, attenuation is 7.3 dB/1000 ft. max and Near-End Crosstalk (NEXT) is a minimum 41 dB per 100 feet. At 4 MHz, attenuation is 16 dB/1000 ft. max and NEXT is a minimum 32 dB per 1000 feet. At 10 MHz, attenuation is 27 dB/1000 ft. max and NEXT is a minimum 26 dB per 1000 feet. At 16 MHz, attenuation is 36 dB/1000 ft. max and NEXT is a minimum 32 dB per 1000 feet.
Category 4 Cable
This extended specification covers all Category 3 requirements and can also support transmissions up to 20 MHz, for data and voice networks including 16-Mbps Token Ring, and 100Base-T4.
Specifications: capacitance is 15 pF, impedance is 100 ± 15 ohms. At 1 MHz, attenuation is 6 dB/1000 ft. max and NEXT is a minimum 56 dB per 1000 feet. At 4 MHz, attenuation is 12 dB/1000 ft. max and NEXT is a minimum 47 dB per 100 feet. At 10 MHz, attenuation is 20 dB/1000 ft. max and NEXT is a minimum 41 dB per 1000 feet. At 16 MHz, attenuation is 25 dB/1000 ft. max and NEXT is a minimum 38 dB per 1000 feet. At 20 MHz, attenuation is 31 dB/1000 ft. max and NEXT is a minimum 36 dB per 1000 feet.
Category 5 Cable
It should be fully compliant with EIA/TIA 568 specs for 100-MHz UTP premise wiring. Category 5 cables can support data and voice networks including: 100-Mbps twisted-pair Fast Ethernet (100Base-TX and 100Base-T4 ), ATM (Asynchronous Transfer Mode), TPDDI (Twisted Pair Distributed Data Interface), high-speed RS-232, and ANSI 3XT9.5 networks. Category 5 cable is the recommended choice for most installation because it offers the most resistance to the four CAIN raisers that afflict networks. It is backwards-compatible with installations that include Category 4 and 3 cables.
For plenum installation, specify only cables with all inner pairs shielded with fire-resistant materials, such as Teflon. Cable jackets should have a high temperature rating. Make sure any currently installed cable meets the highest specification.
Specifications: capacitance is 14 pF, impedance is 100 ± 15 ohms. At 4 MHz, attenuation is 13 dB/1000 ft. max and NEXT is a minimum 53 dB per 100 feet. At 10 MHz, attenuation is 20 dB/1000 ft. max and NEXT is a minimum 47 dB per 1000 feet. At 20 MHz, attenuation is 28 dB/1000 ft. max and NEXT is a minimum 42 dB per 1000 feet. At 100 MHz, attenuation is 67 dB/1000 ft. max and NEXT is a minimum 32 dB per 1000 feet. You can always substitute higher category components than are required by the network; however, substituting lower category components will lower the performance of the entire circuit to that lower category.
Note: PC What's The Problem? includes identification, test, repair and installation suggestions.
CCIR-601
Consultative Committee, International Radio standard defines a 720 by 480 pixel image format for high-quality TV image; it was included in the MPEG-2 specifications. Compare with other video standards: CIF, QCIF, QSIF and SIF.
CCS (Contact start/stop)
These drives are designed for desktop and portable computers Their heads are automatically locked-down on the LZs when drive power is lost and/or when the appropriate park and lock ("park-the-heads") command is received. This should be the only time a head touches the platter media. The drives designed for laptop and notebook computers must be able to survive mechanical shocks both while powered on and powered off. A further consideration is energy-saving requirement.
CD (or CD-ROM)
This is a read-only compactdisk format similar to single-layer prerecorded audio CDs. CD-r, a write-once technology, enables a 5.25" optical disk to be written to incrementally, and is backward compatible with CD-ROM.
When purchasing, consider drives with a MultiRead compatible logo. Also reference: DVD.
CD Label
The label on the non-data "front" of a CD which is fixed to the media by screen printing and sometimes by offset printing.
CD Mastering
The first step in the CD manufacturing process. A laser beam recorder (LBR) is used to transfer data onto a glass disc which is coated with a photoresist. This disc is known as a glass master.
CD-2X
Double-speed CD drive with a potential data transfer rate of 300KBps, but realistically between 150 to 200KBps.
CD-4X
Quad-speed CD drive with a potential transfer rate of 600KBps, but realistically between 300 to 450KBps. CD-6X Six-speed CD drive with a potential transfer rate of 900KBps, but realistically between 450 to 600KBps. CD-8X, an eight-speed CD drive with a realistic data transfer rate between 300 to 450KBps. CD-10X a ten-speed CD drive with 3MBps transfer rate. Other references: Video-CD and PD-CD. Also CD-12x and CD-24x. Note: PC What's The Problem includes identification, test, repair and installation suggestions.
CD-E
CD-Erasable is a rewritable CD process. The new O-ROM drives overwrite specially formatted read-only 3.5" disks. Access and transfer rates are less than hard drives, i.e., 40 millisecond (ms) access and 120 M storage). "Multifunction" CD-E drives can also read and write to both CD-R and CDs; however, pre-1996 model CD-ROM drives can not read CD-E disks.
CD-I
CD interactive drive.
CD-P
Compatible with Kodak Photo CD standard.
CD-R
CD-Recordable or "RCD" These recordable CD drives read both CD-WORMs and CD-ROMs. Considered as the "CD-WORM-2" (write-once-read-many-times) process, CD-R and WORM CDs cannot be erased. CD-R drives support "multifunction" formats. Sections of the CD can be formatted to work with different operating systems. WORM drives record data sequentially on a specially formatted data-storage CD. Because of this archiving, CDs can only support a single operating system. A WORM CD's capacity is great enough to store multiple versions of the same document. If so, then previously saved versions can be accessed and/or edited and saved again as newer versions.
CD-RFS. While most CD-R drives require the writing or "burning" of an entire CD at a time, Sony's CD-R filing system (CD-RFS) drives also write data in small packets, similar to the magnetic media in floppy and hard drives. A "history" function permits the undeleting of the hidden deleted files. For use on non-RFS drives, a utility can be used to "freeze" the data for full compatibility. CD-ROM is a single-speed CD drive with a potential 150 Kilobytes-per-second (KBps) data transfer rate, but realistically about 90KBps.
CD recorders provides at least one of these formats: ISO 9660 (DOS/Windows and MacOS), HFS (MacOS-specific), UDF (the ISO 13346 universal data format), CD audio (with data), CD-I, CD-P, and WORM.
When purchasing, consider drives with a MultiRead compatible logo.
CDRAM
Cache Dynamic RAM chips (from Mitsubishi).
CD-V
Compatible with Video CD standard.
CD-XA
CD-ROM with extended architecture combining CD data with interleaved compressed audio or video.
CD-Extra
Formerly CD Plus, was endorsed by Microsoft for multimedia content.
Center Frequency
The midpoint in the passband, (a.k.a., Normal Frequency).
Cerment pots
They are referenced with the other resistors.
CF
The "half-size" (PCMCIA-ATA) card standard, created by the Compact Flash Association, to provide data storage for palmtop, notebook and desktop computers and digital cameras. A Compact Flash solidstate card is smaller than a PCMCIA Type II (PC Card-2) device. An interface adapter is available for PCMCIA ATA Type II and Type III slots so they can be used to access CF data storage devices. Compatibility is a hardware issue.
Newer high-capacity CD formats include the double-sided, 8GB, Super Density (SD) recording technique and the single-sided, two level, 3.7GB, Multimedia Compact Disk (MMCD).
CGS
Inside a processor chip, the Coefficient Generation System is part of the Arithmetic Unit's Functions Evaluation Unit. CGS is used to generate Fast Fourier Transform (FFT), Heterodyne Beamforming, and user-supplied coefficients.
Characteristic Impedance
A cable specification. The total resistance, measured in ohms, to the flow of alternating current (AC) that a wire would exhibit if it was infinitely long. Note, mismatches in impedance, along a cable, cause distortions and reflections.
CIF
Common Interface Format is a 352 by 288 pixel format for 29.97 frames per second videoconferencing. Compare with other video standards: CCIR, QCIF, QSIF and SIF.
Client
A computer that has access to services over a computer network. The computer providing the services is a server. Note: in an X-11 environment, the meanings of client and server are reversed.
Client-Server Architecture
An information-passing scheme that works as follows: a client program, such as Mosaic, sends a request to a server. The server takes the request, disconnects from the client and processes the request. When the request is processed, the server reconnects to the client program and the information is transferred to the client. This architecture differs from traditional Internet databases where the client connects to the server and runs the program from the remote site. Note: in an X-11 environment, the meanings of client and server are reversed.
Clock crystal
A computer's systemboard component that sets the frequency of signals passing in the circuit between each component and the microprocessor (or CPU). It determines the specific number of commands that the CPU can process within a specific time frame. Because of variances in CPU manufacturing, the typical crystal operates the CPU at less than 100 percent of its functional limits. This is considered a margin of safety. While replacing the original crystal with a faster one--matched to the CPU's maximum functionality--the higher speed and operating temperature can result in damage to the CPU and/or other components.
CM
A processor chip's Cache Memory.
CM
Coherent Memory.
CMA
A processor chip's Cache Memory Address.
CMAG
A processor chip's Cache Memory Address Generator.
CMMU
Cache/Memory Management Units connect and manage the P Bus and M bus inside a RISC processor.
Coax Cable
A round, single-wire cable. It is the standard for delivering cable TV signals to a TV set (that is "cable-ready") or to a cable descrambler "box."
Cold Weld
Dissimilar metals are pressed together under great pressure to form one metal.
CHECKSUM
An error-checking protocol. It detects single and some multi-bit errors by adding all the bytes in a block of data together; this total is sent along with a character's defining data-bits. The receiving device also calculates a total for bits-received and compares its total to the received total. If the two totals are not equal&emdash;an error has occurred&emdash;it signals: "send the character again."
Combining Modulations
For high-speed transmissions, some modems combine different types of modulation to sending more bits-per-"baud." (Baud measures pulse-modulations per second.) Sometimes without the need for a greater "bandwidth" pipeline. For example, FSK sends 1 bit per baud. Four-level PSK sends 2 bits per baud.
Quad Amplitude Modulation (QAM) combines up to four different phases with up to four different amplitudes (pulse-wave-heights) to send (16 combinations of) 4 bits per baud.
A 2400-baud modem, using QAM, can send 9600 bits per second. Increased amplitude piggybacks 2 bits into a single wave-pulse. Frequency (the distance between pulses) makes this possible. Piggybacked pulses with a "0" first digit, have less distance between them than those with a "1."
Choke inductors
They are referenced with other inductors.
Co-Mem PCI controller chip
This 208-pin PQFP-packaged chip is available from Anchor Chips, San Diego, CA. It creates an intelligent PCI-bus to support expansionboards with onboard microprocessors (including most 8-, 16-, and 32-bit microprocessors from Intel and Motorola). The chip includes 8KByte instruction and data caches with 60-ns access that buffer PCI-bus burst data transfers. This cache appears in the microprocessor board's program-memory address space; as well as, acting as a cache for the system's "main memory" RAM making it available for the board's microprocessor. The chip's cache controller maintains 1KB instruction-cache pages, 512-byte data-cache pages, an a 16MB virtual memory space. To hold interrupt routines ready, Individual pages can be locked.
The chip has a direct-access connection to the PCI bus so that the microprocessor can communicate with other peripherals on the bus.
The Co-Mem chip requires a serial ROM chip to initialize itself after a reset.
Coil inductors
They are referenced with other inductors.
Computer Cable
Connecting computers and their peripheral devices require cables that meet or exceed the precise signal characteristics of RS-232, RS-422, RS-423, and RS-449. These data-grade cables are constructed of materials determined by functions. Coaxial, twin-axial, multiple-pair cables have wires that may be individually shielded, as well as shielding over all wires.
Other references: Cables and connectors, Instrument and Communications Cable, Plenum Cable, and EIA/TIA Category Standard unshielded twisted-pair (UTP) cables.
Note: PC What's The Problem? includes identification, test, repair and replacement suggestions.
Configuration
This is a general-purpose computer term that can refer to the way you have your computer set up. It is also used to describe the total combination of hardware components that make up a computer system and the software settings that allow various hardware components of a computer system to communicate with one another.
CP
A (RISC) processor chip's Control Processor which controls the overall operation of the chip's arithmetic or IO cluster.
CR
Inside a processor chip, the sequencer's Control Register.
Crosstalk
A cable specification of the electrical interference that results when one wire's signal affects another wire's signal. For example, the wires in an unshielded twisted-pair (UTP) cable, because of its lack of shielding, are more likely to be effected than wires in a shielded twisted-pair (STP) cable.
CRC
Cyclical Redundancy Check detects errors in data transmissions by an algorithmic calculation of parity bits added to each byte.
Cylinder-Tracks ( Cyl )
Typically, hard drives have many spinning platters, which are double-sided "disks". A floating head is positioned to read from and write to each side. All read/write head are extended to the same position over their associated sides, forming a vertical "stack of tracks" that looks like and is termed a "cylinder."
Cylinder-tracks are numbered from the outer rim towards the center hub starting from the number 0. Data is stored in this order; with the highest numbered cylinder as the last to be filled. Most BIOSs (that work with the Intel CPUs) support a maximum of 1024 cylinder-tracks; the last one is number 1023. Many drives reserve this cylinder-track as a Landing Zone for the read/write heads.
Most hard drives have between 312 and 1024 cylinder-tracks. This number is predetermined by both the magnetic pattern on the platter's data storage media, and by the calibrations of the mechanism that moves the actuator-arm with its attached read/write head. These Stepper Motor and Voice Coil mechanisms move all heads, at the same time, to the same position over their assigned platters. .
References are samples only. Each one is presented in greater detail in the
Technical Research Assistant for 2001
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