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.ASRAutomatic Send Receive--any keyboard terminal capable of generating amessage into off-line storage for later transmission; includespaper-tape telex machines as well as microcomputers.AsynchronousDescription of communications which rely on 'start' and 'stop' bitsto synchronise originator and receiver of data--hence asynchrnousprotocols, channels, modems, terminals etc.** Page 117Backward channelSupervisory channel, not used as main channel of communication; inviewdata the 75 baud back from the user to the host.file:///E|/Books/Hackers Handbook.htm (110 of 133) [11/28/2000 5:58:50 AM] Hacker's HandbookBaudMeasure of the signalling rate on a data channel, number ofsignalling elements per second.BasebandModulation is direct on the comms line rather than using audio orradio frequencies; used in some local area networks.A baseband or'short-haul' modem can be used to link computers in adjacent offices,but not over telephone lines.Baudot5-bit data code used in telegraphy, telex and RTTY--also known asInternational Telegraph Alphabet No 2.Bell(1) non-printing character which sounds a bell or bleep, usuallyenabled by G; (2) Common name for US phone company and, inthis context, specifiers for a number of data standards and services,e.g.Bell 103a, 202a, 212a, etc--see Appendix VBit Binary digitvalue 0 or 1.BroadbandBroadband data channels have a wider bandwidth than ordinarytelephone circuits--12 times in fact, to give a bandwidth of 48kHz,over which may simultaneous high-speed data transfers can take place.Broadcast serviceData service in which all users receive the same informationsimultaneously, without the opportunity to interrogate or query;e.g.news services like AP, Reuters News, UPI etc.See also on-lineservice.BisynchronousIBM protocol involving synchronous transmission of binary coded data.** Page 118BLAISEBritish Library Automated Information Service-- substantialbibliographic on-line host.BREAKNon-printing character used in some data transmission protocols andfound on some terminals--can often be regenerated by using 1.BSCBinary Synchronous Communications--see bisynchronous.I ByteGroup of bits (8) representing one data character.Call acceptIn packet-switching, the packet that confirms the party is willing tofile:///E|/Books/Hackers Handbook.htm (111 of 133) [11/28/2000 5:58:50 AM] Hacker's Handbookproceed with the call.Call redirectionIn packet-switching, allows call to be automatically redirected fromoriginal address to another, nominated address.Call requestIn packet-switching, packet sent to initiate a datacall.CCITTComite Consultatif International Telephonique et Telegraphique--committee of International Telecommunications Union which setsinternational comms standards.Only the US fails to follow itsrecommendations in terms of modem tones, preferring 'Bell' tones.TheCCITT also sets such standards as V21, 24, X25 etc.Character terminalIn packet-switching, a terminal which can only access via a PAD.ClusterWhen two or more terminals are connected to a data channel at asingle point.Common CarrierA telecommunications resource providing facilities to the public.** Page 119Connect-timeLength of time connected to a remote computer, often the measure ofpayment.Contrast with cpu time or cpu units, which measures howmuch 'effort' the host put into the communication.CPSCharacters Per Second.Cpu TimeIn an on-line session, the amount of time the central processoractually spends on the interaction process, as opposed to connect-time; either can be used as the basis of tariffing.CRCCyclic Redundancy Check--error detection method.CUGClosed User Group--group of users/terminals who enjoy privacy withrespect to a public service.DatacallIn packet-switching, an ordinary call, sometimes called a 'switchedvirtual call'.DatalineIn packet-switching, dedicated line between customer's terminal andpacket-switch exchange (PSE).file:///E|/Books/Hackers Handbook.htm (112 of 133) [11/28/2000 5:58:50 AM] Hacker's HandbookDCEData Circuit-terminating Equipment--officialese for modems.DTEData Terminal Equipment--officialese for computers.EBCDICExtended Binary Coded Decimal Interchange Code--IBM's alternative toASCII, based on an 8-bit code, usually transmitted synchronously.256characters are available.EmulatorSoftware/hardware set-up which makes one device mimic another, e.g [ Pobierz całość w formacie PDF ]