Summary

22 plain old telephone serviceplain old telephone service (POTS) The regularphone system, which typically uses analog signals totransmit voice and data. Sometimes called the PublicSwitched Telephone Network (PSTN).platen A large roller in a dot-matrix printer thatapplies pressure to keep the paper from slipping. Ifmultiple-copy paper is used, the platen gap can beadjusted to the paper’s thickness.plug-and-play Technology that allows a computerto automatically configure the devices that connect toit.point of presence (POP) The point of interconnectionbetween the communication facilities providedby the telephone company and the building’s maindistribution facility.port replicator A fixed base unit in which a laptopis inserted and can connect to peripheral devices.power adaptor A device that transforms AC to DCto provide electricity to the computer and charge thebattery.power buttonoff.A control that turns a device on andpower cable An external cable consisting of colorcodedconductors that transfer electricity to a computerand attached electrical devices.power line communication (PLC) A communicationmethod that uses power distribution wires (localelectric grid) to send and receive data.power on indicator LEDlaptop’s on/off status.A light that shows thepower-on self-test (POST) A diagnostic test ofmemory and hardware when the system is powered up.power supply Converts AC (alternating current)into the lower voltages of DC (direct current), whichpowers all the computer’s components. Power suppliesare rated in watts.presentation layer Layer 6 of the Open SystemsInterconnection (OSI) reference model. This layerensures that information sent by the application layerof one system can be read by the application layer ofanother. The presentation layer is also concernedwith the data structures used by programs and thereforenegotiates data transfer syntax for the applicationlayer. Corresponds roughly with the presentationservices layer of the Systems Network Architecture(SNA) model. The OSI reference model includes theapplication layer, presentation layer, session layer,transport layer, network layer, data link layer, andphysical layer.preventive maintenance Regular and systematicinspection, cleaning, and replacement of worn parts,materials, and systems.preventive maintenance policy A detailed programthat determines maintenance timing, the type ofmaintenance performed, and the specifics of how themaintenance plan is carried out.primary corona wire A voltage device that erasesthe charge on the printing drum. Also called the gridor conditioning roller.primary partition The first partition on a harddrive. A primary partition cannot be subdivided intosmaller sections.Primary Rate Interface (PRI) An ISDN interfaceto primary rate access. Primary rate access consistsof a single 64-Kbps D channel plus 23 (T1) or 30(E1) B channels for voice or data. Compare to BRI.