CSU. Channel service unit, a piece of electronic equipment found near the demarcation point used to terminate the digital service at the customers premises.
It serves as a point of diagnosis and testing.
DCE. Data communications equipment, the electronic equipment that establishes, maintains, and terminates a connection to a network. The DCE may be a part of a modem, but not necessarily.
de facto Standard. A standard because it is widely accepted in the industry, a standard from fact.
de jure Standard. A standard because it has been approved by a standards organization, a standard by right.
Distribution Frame. A physical structure that holds telephone distribution blocks, either rack mounted or wall mounted. The distribution blocks on the buildings main distribution frame serve to connect wires from the buildings PBX, or the telephone companys central office, to the remote distribution frames or to the local extensions through cross connects.
Duct. Duct, or conduit, is used to protect and install cabling. Types include electrical??metallic tubing (EMT), intermediate metallic tubing (IMC), rigid galva nized steel (RGS), electrical nonmetallic tubing (ENT), polyvinyl chloride (PVC) schedule 40, and polyvinyl chloride (PVC) thin wall. Innerduct is a corrugated PVC, or plenum-rated material, used to protect fiberoptic cables or to group fiber cables in a duct; i.e., three 11â„4-in innerducts may be installed in one 4-in duct.
DSU. Data service unit, electronic equipment that interfaces a digital service network such as a T1 carrier to the DCE (data communications equipment). DSUs are usually located in the main communications closet on the wall or in a rack.
DTE. Data terminal equipment, the source or destination of signals on a network.
Data terminals or display terminals that had no integral computing power were used as the destination of signals from mainframe computers. Data terminals became known as dumb terminals as personal computers were developed. PCs are smart DTEs.
Edge Equipment. Electronic equipment that interfaces ATM and Ethernet networks.
EIA. Electronic Industries Alliance, a trade organization representing the United States high-technology community.
Electronic Industries Association. A standards-writing body.
ELAN. Emulated LAN on an ATM network.
Entrance Facility. The entrance to the building for communications cables, including the point at the wall or floor and the conduit or path to the buildings main communications room.
Entrance Facility, Fiberoptic. The box in a buildings main communications room where the outside-plant cable is spliced or connected to the buildings fiberoptic cable.
Ethernet. A local area network, LAN, as defined by Standard IEEE 802.3, where computers or stations are connected together. The most common arrangement today is where twisted-pair cable, CAT 5 or CAT 5e, connects PCs to network hubs with speeds of 10 Mbps and 100 Mbps (fast Ethernet). Thick coaxial cable, thin coaxial cable, and fiberoptic cable may also be used. Faster speeds of 1000 Mbps will be common soon.
FDDI. Fiber distributed data interface, an ANSI standard for token ring networks using fiberoptic cabling and special FDDI connectors and patch panels.
Fiberoptic Connectors. Types include SC, ST, FC, Biconic, FDDI, ESCON, MTRJ, LC, and Volition.
Fiberoptic Cable. Fiberoptic cable comes in two main types, multimode and single mode. Multimode fibers are sized by the core dimension and the cladding dimension. The most common multimode cable is the 62.5/125 micron. An enhanced version is the 50/125 micron. Hybrid cables are available with varying counts of multimode and single-mode fibers, such as 12/6 cable or 24/12 cable.
File Server. A modified computer or PC that holds programs and files for common use by the PCs on the network. Modifications may include multiple processors, redundant power supplies, RAID (redundant array of inexpensive disks) drives, etc. Servers may be classified by function such as a mail server or drawing file server.
Frame Relay. A high-speed protocol used in WANs. A frame alignment signal is sent as well as the frames. Frames are actually consecutive time slots.
FM. Factory Mutual, a building and industrial insurance underwriter who provides guidance and approval of building products. FM also has a nonprofit research center and writes standards.
Gateway. Electronic equipment or computer that converts protocol from one network or system to another.
Gigabit Ethernet. Ethernet network transmitting over 1 Gbps or 1000 Mbps.
Hub. A piece of electronic LAN equipment located in a communications closet that connects to the desk PCs. Like a wheel, the hub is at the center, the spokes are the cabling to desk PCs. Hubs may be intelligent or dumb. If a hub is not labeled as intelligent, it is dumb. An intelligent hub has processing electronics to manage the network, sometimes to bridge, route, and switch. If the hub is too smart, it is not a hub, it is a switch. The industry is increasing the use of switches and decreasing the use of hubs.
Interface. A device, or group of devices, that allow two incompatible systems to communicate. A protocol that allows two incompatible systems to communicate.
ISDN. Integrated Services Digital Network is a digital transmission standard and service. Basic-rate ISDN provides two switched B channels (64 kbps for voice and data) and one D channel (16 kbps for control). Primary-rate ISDN provides 23 B channels and one D channel for a capacity of 1.544 Mbps. ISDN may be provided over a T1 line (two twisted-pair cables). ISDN was never embraced by the public or the industry; it was too confusing. The most common use in commercial buildings is for videoteleconferencing where a two-pair ISDN cable is terminated in a conference room. An ISDN terminal adapter is used to connect to a computer and phone. The owner will hire a vendor to provide and set up a videoteleconferencing package. Some training and user assistance is usually provided.
IEC. International Electrotechnical Commission, a standards-making body.
IEEE. Institute of Electrical and Electronic Engineers, a standards-making body.
IEEE 802.2. LAN protocol standard, written by IEEE.
IEEE 802.3. Ethernet physical layer standard, written by IEEE.
Ink-jet. A type of printer that sprays ink onto the page. Ink-jet printers are used in offices, mostly as personal printers connected directly to the PC. They provide inexpensive black and white and color prints.
IT. Information Technology.
Jack. A female communications connector into which a plug is inserted. Jacks fall into three groups: voice, data, and network channel equipment (networkchannel equipment jacks are not discussed here). Jacks are found in office wall plates, in office system furniture, on the back of PCs, on patch panels in the communications closet, and on the network equipment. The most common data jack is the eight-position modular jack defined by ANSI/TIA/EIA Standard 568, designated as T568B. A T568A is also defined. The standard defines the position of the cable pairs and their color. Please note that the government publication FIPS PUB 174 only recognizes T568B. If you are renovating an office, look out for re-termination costs.
The most common telephone jack is the USOC six-position modular jack.
