RG-6 coax 75 ohms
RG-8 coax 50 ohms
RG-58 coax 50 ohms
RG-59 coax 75 ohms
RG-62 coax 93 ohms
Cat 5 UTP 100 ohms
Cat 7 UTP 100 ohms
3IBM type 1 Data 150 ohms
Character-Oriented Protocol (Another name for Byte-Oriented Protocol) A X.25 standard protocol used by mainframes that pre-vented data of unlike character sets to be transmitted over communications lines. Newer communications standards are bit-oriented protocols, and are not character or application sensitive. See also Byte-Oriented Protocol.
Character Set The letters and numbers on computer keyboards. Differ-ent standards apply to how the letters and numbers are converted to bi-nary code. The most widely embraced standard for PCs is ASCII
Chip An integrated electronic component. Integration refers to many circuits integrated into one small device.
Chipset A group of microchips in a computer that allows hardware periph-eral devices (such as modems and network interface cards) in PCI and ISA buses to communicate without using the main CPU. This reduces the CPU processing load, thus helping the computer accomplish tasks faster.
Choke Also called a choke coilor RF choke. A coil of wire manufactured with the intent of being a filter that reduces the passing of high frequen-cies through it. For a photo, see RF Choke.
Choke Coil See Choke.
CI (Clear Indication/Clear Request) The packet that is sent when a de-vice on an X.25 network would like to end a call. The other dede-vice confirms the end of the call by sending a CC (Clear Confirm)packet. For a diagram of X.25 packet-level header structure, see X.25 Call-Request Packet.
CIP (Certified Internet Professional) A well-known industry certifi-cation/training program that is offered by Novell and its training part-ners. The CIP is an advanced certification. The prerequisite for the CIP study track is the possession of a CNE rating. This training program is designed to train individuals who will utilize Novell products in net-work/Internet integration. Information regarding Novell training can be found at http://www.education.novell.com.
Circuit 1. Another name for a phone line. There are many types of cir-cuits: digital, analog, T1, and ISDN circuits. 2. An electronic device that receives a given input and converts it into a desirable output. For
in-Circuit 125
stance, a TV converts a transmission input into a picture and sound. A TV can be regarded as one giant circuit or many small circuits.
Circuit Board Any form of electronics parts placement that is on a flat surface.
Circuit Breaker An electronic or electrical device installed in a power-distribution system that disconnects (or turns off) the power when the specified current rating of the circuit breaker is exceeded (Fig. C.24). In most cases, when the specified current in a circuit is exceeded, there is a problem. Circuit breakers disconnect the power before the “problem”
causes other problems (such as fire or power-supply overloading).
126 Circuit Board
Figure C.24 Circuit Breaker. Three 200-Amp Breakers are Shown on a 48-V Distribution Bus
Circuit ID Code The part of a CCS or SS7 signaling message that identi-fies (gives a name to) the circuit that is being established between two points.
Circuit Switching Also referred to as line switching. A long time ago, the line switching was performed by operators sitting in front of a
“cord board.” When a caller wanted to make a call, they would pick up the receiver and an operator would ask “what number, please?” The caller would then tell the operator what number to connect them to, and the operator would plug a cord into the line and connect it to the line (or loop) associated with the number they wanted to call. Today, line switching is performed by “switches.” Switches(also called PBX and key systems) are electronic machines that work similar to the op-erator. Instead of speaking with the operator, the switch and caller
“signal” each other to accomplish the switching function. When the caller goes off hook, the central office switch sends a dial tone. The dial tone is a signal to the caller to “enter number please.” The caller enters digits that signal the number to which they would like to be connected. The central office then sends a “ring” signal to the party being called and a “ring simulation” signal to the calling party, which lets them know that the central-office switch received the digits ok and is signaling the party being called. The party being called then picks up the handset, which activates the switchook and places a 1000-ohm short on the line. The 1000-ohm short signals the central of-fice that the party is ready to receive the call. The central ofof-fice switch then stops the ring signaling and “switches” the talk paths into place for the two callers.
CISC (Complex Instruction Set Computing) Pronounced “Sisk.” A software and hardware architecture method that utilizes a computer’s CPU for the majority of the work load, rather than the software. CISC processors support up to 200 instructions. Most personal computers are made with CISC processors. See alsoRISC.
Cisco-Certified Design Associate (CCDA) This well-known industry certification/training program is offered by Cisco Systems and Cisco Systems training partners. The CCDA program is provided to train indi-viduals for simple-routed LAN, WAN, and switched-LAN networks. More information can be found regarding Cisco Systems training programs through http://www.cisco.com.
Cisco-Certified Design Professional (CCDP) This is a well-known industry certification/training program offered by Cisco Systems and
Cisco-Certified Design Professional (CSDP) 127
Cisco Systems training partners. The CCDP program is provided to train individuals for complex-routed LAN, WAN, and switched-LAN net-works. A CCNA (Cisco-Certified Network Associate) certification must be acquired as a prerequisite for the CCDP program. More infor-mation can be found regarding Cisco Systems training programs through http://www.cisco.com.
Cisco-Certified Internetwork Expert (CCIE) This well-known in-dustry certification/training program is offered by Cisco Systems and Cisco Systems training partners. The CCIE program is the most ad-vanced level of certification for Cisco Systems associates, and is re-garded as a very challenging certification that only the experienced can obtain. The program prerequisites are CCDP, CCNA, and CCNP certifi-cations. This program is offered to provide training and certification to individuals who work in the most-complex networking environments.
More information can be found regarding Cisco Systems training pro-grams at http://www.cisco.com.
Cisco-Certified Network Associate (CCNA) This well-known indus-try certification/training program is offered by Cisco Systems and Cisco Systems training partners. The CCDA program is provided to train indi-viduals for installation and maintenance of routed-LAN, WAN, and switched-LAN networks using Cisco Systems products. The course also lightly covers general LAN and WAN telecommunications. More informa-tion can be found regarding Cisco Systems training programs through http://www.cisco.com.
Cisco-Certified Network Professional (CCNP) This well-known industry certification/training program is offered by Cisco Systems and Cisco Systems training partners. The CCNP is an advanced cer-tification and the prerequisite for the course track is the CCNA (Cisco-Certified Network Associate). The CCNP program is pro-vided to train and certify individuals for complex ISP environments using Cisco Systems networking products. More information can be found regarding Cisco Systems training programs through http://
www.cisco.com.
Citizens Band (CB) See CB.
Cladding One of the two glass sections of a fiber optic (Fig. C.25).
128 Cisco-Certified Internetwork Expert (CCIE)
CLAS (Centrex Line-Assignment Service) A feature offered with centrex service that allows customers to dial into the telephone com-pany’s line-assignment computer system and make changes to where ex-tensions are located, ringing and hunt groups, and which extension numbers or phone numbers are in service.
Class-1 Central Office A centermost point in a large logical network hi-erarchy of long-distance central office switches.
Class-2 Central Office An older term for an network hierarchy of switch points. Central offices are now becoming so well connected in so many ways that they are rapidly becoming either a class-5,4 or a class-1 central office.
Class-3 Central Office An older term for an older network hierarchy of switch points. Central offices are now becoming so well connected in so many ways that they are rapidly becoming either a class-5,4 or a class-1 central office.
Class-4 Central Office A tandem central office or main switch center for an area code. That might also perform class-5 end-connection functions.
Class-5 Central Office A local telephone company central office that connects to end customers.
Class-A IP Address An IP address within the range of 1.0.0.0 and 126.255.255.255. There are a total of 126 Class-A IP addresses. Each Class-A address can support 16,777,216 hosts. Address 127.x.x.x was used during the development of IP, and is not a valid address for network use. Class-A addresses are mostly allocated to and used by very large
Class-A IP Address 129
cladding
core
Figure C.25 Cladding
corporations, governments, and universities to identify their Internet do-main. Internet addresses are assigned by InterNIC.
Class-B IP Address An IP address with the range of 128.0.0.0 to 191.255.255.255. There are a total of 16,384 Class-B IP addresses. Each Class-B address can support 65,534 hosts. Class-B addresses are used by medium to large corporations to identify their Internet domain. Internet addresses are assigned by InterNIC.
Class-C IP Address An IP address with the range of 192.0.0.0 to 223.255.255.255. There are a total of 2,097,152 possible Class-C net-works. Each Class-C address can support up to 254 hosts. Class-C ad-dresses are used by small corporations to identify their Internet domain.
Internet addresses are assigned by InterNIC.
Class-D IP Address An IP address with the range of 224.0.0.0 to 239.255.255.255 are used for Multicast addressing. Such modern routing protocols as ICMP (Internet Control Message Protocol) and Cisco’s IGRP (Interior Gateway Routing Protocol)are capable of recognizing multicast addresses. See also IP Multicast.Class-D addresses are not as-signed to specific hosts, but to groups of hosts on a network. Multicast addresses are assigned by the administrator of the Internetwork.
Class-E IP Address An IP address with the range of 240.0.0.0 to 255.255.255.254. These addresses are reserved for special-purpose and future addressing modes. The address 255.255.255.255 is the dejure standard broadcast address. Class-E addresses are not assigned in a net-work.
Class of Service (COS) A type of telephone service or telephone line pur-chased from a telephone company. Some class-of-service examples follow:
• 1FR One flat rate, residential. What most residential customers have.
• 1MR One measured rate, residential. Where the line has a low monthly fee, but each call beyond a certain number costs up to an additional 10 cents.
• 1FB One flat rate, business. What most small-business customers have.
• 1F4 A four-user party line.
Clear Channel See CCC.
Clear To Send (CTS) SeeCTS.
Cleaving A term used in the splicing fiber optic that means to cut the end of the fiber clean at 90 degrees, with minimal rough edges, in preparation
130 Class-B IP Address
for a fusion splice. Where a mechanical splice is involved, the end of the fiber optic is hand-smoothed with a polishing puck before splicing.
Client-Server Environment A type of network environment with re-questers (clients) and providers (servers). A service requested could be for processing, a file, or an application.
Climbers What telecommunications and power company personnel wear to climb wooden telephone and power poles. The official name for these de-vices are lineman’s climbers.They are also called spurs, hooks, and gaffs.
They consist of a steel shank with straps so that it can be strapped to a per-son’s leg. On the inside of the shank is a spike that is used to stab into the pole. The climbers in Fig. C.26 were manufactured by Buckingham Mfg. Inc.
Clipper 131
Figure C.26 Lineman’s Climbers
Climbing Belt Used by communications/power/construction personnel to harness themselves to telephone/power poles or tower structures.
Also called a safety beltand body belt. For a photo, see Safety Belt.
Clipper A circuit that takes a sine-wave input, like that of a timing oscil-lator and converts it into a square-wave form that can be used as a clock signal for a digital device. A clipper circuit is simply an amplifier that is
over driven into saturation, which causes a form of distortion (in this case, useful) called clipping.
Clipping You can experience clipping by turning up the volume on an in-expensive stereo and noticing that at a certain point, the sound repro-duction is unclear (Fig. C.27). First, the bass tones are affected because they take the most energy to reproduce. At this point in increasing the volume, the sound level is not getting any louder, the signal is only be-coming more corrupted. Technically, clippingis a form of signal distor-tion where the amplificadistor-tion of a signal in volts exceeds the saturadistor-tion bias voltage of the transistor in an amplifier. In other words, the peak and negative peaks of the output waveform are not included because the am-plifier is not capable of amplifying the input anymore.
132 Clipping
Maximum amplification
Input signal maximum output
Without clipping over driven output
The part of the wave that is above and below the maximum amplification is not reproduced it is “clipped off”.
Figure C.27 Clipping
CLLI Code An 11-digit alphanumeric code that identifies physical loca-tions in the phone network. Almost every significant building in the United States has a CLLI code. It is pronounced “silly code.”
CLNP (Connectionless Network Protocol) An OSI (Open Systems Interconnect)network layer protocol that does not require a circuit to be established before data is transmitted. The basis of a connectionless protocol is that there is no direct RTS (Request to Send) or ACK (Acknowledge)type of signaling, thus, no direct connection. See also CLNS.
CLNS (Connectionless Network Service) An OSI (Open Systems Interconnect)network layer protocol that does not require a circuit to be established before data is transmitted. CLNS works as a part of or with other protocols that reside in the network layer and other layers. All packets are sent independently of each other. See also CLNP.
Clock A device that provides timing pulses for communications equip-ment or devices within a computer the same way that a metronome pro-vides a steady time for a musical band (Fig. C.28).
Clone Fraud 133
Figure C.28 Clock Source (Distributed)
Clock Bias The difference between a clock’s output and true universal time. Simply put, how far off a piece of equipment’s timing is. It is usually measured in positive or negative microseconds.
Clocking See Clock.
Clone Fraud The crime of finding cellular ID codes by monitoring cellu-lar transmissions (with expensive cellucellu-lar equipment), then copying the code to another cellular phone and making calls with it. The airtime for the copied phone (the clone) is billed to the original phone.
Closure A casing, pedestal, or cabinet used to house open ends or splices in outside cable plant. Closures mostly refer to splices. Different names for buried splice closures or enclosures are Xaga and Cold-N-Close. A popular aerial splice closure is the TRAC closure.
CLP (Cell Loss Priority) An ATM (Asynchronous Transfer Mode)cell header bit that determines the probability of that cell being dropped if the network becomes congested. Cells with CLP 0 are insured traffic, which are unlikely to be dropped. Cells with CLP 1 are best-effort traffic, which will be dropped in congested conditions in order to free up resources for in-sured traffic. Whether cells are dropped interdepends on many congestion-handling parameters within the ATM network. See also Constant Bit Rate.
CLR (Cell Loss Ratio) An ATM (Asynchronous Transfer Mode) quality-of-service parameter that might be implemented on a subscribed connec-tion. The CLR is equal to the ratio of discarded data cells to successfully transported data cells. See also Cell Loss Priorityand Insured Rate.
Cluster Controller 1. Generally, an intelligent device that provides the data communications management and control for a cluster of terminals to a data link. 2. In IBM SNA (System Network Architecture),a pro-grammable device that controls the input/output operations of attached devices. Typically, it is an IBM 3174 or 3274 or newer type of device.
CMOS (Complementary Metal-Oxide Semiconductor) The reason why many computer and other high-speed components are static sensi-tive. Complementary Metal-Oxide Semiconductor’s largest advantage over TTL (Transistor-Transistor Logic) is their low power consumption (less than 1⁄10of TTL), they switch on without drawing very much current, in contrast to TTL. Since very little current is drawn, very little power is consumed and very little heat is given off. This allows the devices to be much smaller.
CNA (Certified Novell Administrator) A well-known industry certifi-cation/training program offered by Novell and its training partners. The CNA program is designed to educate those who will maintain and ad-minister installed Novell networking products.
CNE (Certified Novell Engineer) A well-known industry certifica-tion/training program that is offered by Novell and its training partners.
The CNE study track is designed to train individuals who will provide complex technical support and installation of Novell products. The CNE program is an in-depth study program that covers Novell specific prod-ucts and data networking as a whole. An additional level to this certifica-tion called Master CNE. Information regarding Novell training can be found at http://www.education.novell.com.
134 Closure
CNX (Certified Network Expert) A well-known industry certification that is offered by the CNX Consortium. It provides an intense training track for LAN and MAN networking in multivendor environments. More information can be found regarding the CNX certification program at http://www.cnx.org.
CO An abbreviation for an RBOC Central Office. CLEC’s often refer to their central switching offices as Type One Nodes.
Coax (coaxial cable) A shielded copper transmission media that has one central conductor surrounded by a dielectric (Fig. C.29). It comes in sev-eral varieties. For a listing of the different characteristic impedances of coax types, see Characteristic Impedance.
Code Blocking 135
N-TYPE CONNECTOR
BNC CONNECTOR
F CONNECTOR
Figure C.29 Coaxial Connector Types: F (Left), BNC (Center), and N Type (Right)
COBOL (Common Business Oriented Language) A computer program-ming language.
Code Blocking A feature of a telecommunications switch that enables it to restrict specific extensions from dialing long distance or just a specific group of area codes. Local telephone companies use this feature to re-strict a customer’s long-distance calling ability from their phone if they have a poor credit rating and were not able to make a deposit for their phone service. This feature is frequently used in PBX applications to pre-vent employees from making any long-distance calls.
CODEC (Coder Decoder) Another name for an analog-to-digital (and digital-to-analog) converter.
Coherent Light Light that consists of only one frequency or very close to one frequency. Coherent light looks to the human eye as a very pure color. Lasers and LEDs(Light-Emitting Diodes, like the one that lights when the hard drive in your computer is running) emit light that is very close to being coherent. A light bulb emits noncoherent light, which con-sists of many colors and wavelengths.
Coil In telecommunications, a coilrefers to a load coil, which is a voice-amplifying device for twisted-pair wire. A load coil is usually placed on each twisted pair used for a voice line every 3000 feet past a central office. Coils are usually located in vaults, with twisted-pair splices. Other coils, used for other electronic applications are usually referred to as choke coils.
Coin-Operated Telephone A telephone that can be installed, operated, and maintained by a local phone company or purchased from a telephone-equipment distributor, connected to a local phone line and maintained by
Coin-Operated Telephone A telephone that can be installed, operated, and maintained by a local phone company or purchased from a telephone-equipment distributor, connected to a local phone line and maintained by