Phreaker's Dictionary A & A BUREAU--Abuse and annoyance bureau. The personnel in this line of work spend their time helping customers get rid of nuts, obscene callers, harassing collectors, etc. ACCESS--The existence of paths within a network from an input terminal to a set of output terminals in the absence of traffic is indicated by the term, ACCESS. Full access permits connecting to all output terminals by unique paths; multiple access indicates that all output terminals can be reached in more than one way; partial access refers to the ability to reach only a fraction of the output terminals. ACCESSIBILITY--(availability)--The number of trunks of the required route in a switching network which can be reached from an inlet. ADAPTOR--A device designed to switch a number of voice-frequency telephone channels coming from a non-time-division switching system to a time-division multiplex highway. ALTERNATE ROUTING--A procedure by which several routes involve different switching stages or switching networks. Usually the route having the fewest switching stages is tested first. ANALOG TRANSMISSION--The transmission of continuously variable signals rather than descretely variable signals. Prior to the use of digital encoding and PCM, it was the only way of transmitting voice signals over telephone channels. AREA CODE--A three-digit prefix dialed ahead of the normal seven-digit telephone number to permit direct distance dialing. ASYNCHRONOUS SYSTEM--A system in which the transmission of each information character is individually synchronized usually by the use of start and stop elements. AVERAGE HOLDING TIME--The average duration of a call expressed in seconds or minutes. BIT--The smallest binary unit of information. A contraction of the words binary digit. BIT RATE--The rate or speed at which bits are transmitted. Bits per second is a common measure. BLOCKING (CONGESTION)--A condition where the immediate establishment of a new connection is impossible due to the lack of available paths, or the inability to interconnect two idle network terminals because some of the applicable links between them are used for other connections. BOOLEAN ALGEBRA--A form of nonquantitative algebra for dealing with logic funtions, originally expressed by British mathematician George Boole (1815-1864). B.O.S.--Business Office Supervisor. She's the boss to the service reps. BROADBAND EXCHANGE (BEX)--Public switched communication system featuring full duplex (FDX) connections of various bandwidths. A Western Union facility. B.S.I.--Business Services Instructor. A traffice employee who will come out and teach you how to use your phone system. BUSY HOUR--An uninterrupted period of 60 minutes in which the total traffic of a sample is a maximum. BYTE--A unit of information in electronic computer terminology consisting of 8 bits, referred to as extended binary coded decimal information of an EBCDIC code. CALL CONGESTION RATIO--The ratio of the time during which congestion exists to the total time considered. It is an estimate of the probability that an external observer will find a system in a congested condition. CALLING RATE--Average calls per subscriber per hour. CALL STORE--The memory section of a stored program control switching system in which temporary information used in the processing of calls through the exchange is contained. It is also referred to as the Process Store. CENTRAL OFFICE--Exchanges where subscriber lines and private branch exchange lines terminate. There they are switched to provide the desired connection with other subscribers. Such an exchange is called an end office and is designated as a Class 5 office in the U.S. CENTRAL PROCESSOR--The main computer element of a stored program control switching system, which under the direction of the stored program establishes switching network connections and also monitors and analyzes the system to insure proper operation. Routine process testing, maintenance and administrative funtions are also carried out. CENTREX--A PABX system in which the switching equipment is located centrally and away form the location being served. Direct inward dialing (DID) and direct outward dialing (DOD) as well as automatic number identification (ANI) are provided by such a system. CHARACTERS--The elements of a message. One computer character consists of 8 bits or 1 byte and is known as an EBCDIC character. CIRCUIT SWITCHING--Telecommunications switching in which the incoming and outgoing lines are connected by a physical path, as through crosspoints or switch contacts. CLASS OF SERVICE--The services and facilities offered to each individual terminal connected to a system. This information is usually stored with the directory or equipment numbers of the associated terminal, and is accessed by the call processors when a connection is required to or from that terminal. CLOCK--Equipment to provide a time base for a switching system. In time-division switching it is used to control sampling rates, duration of signal digits, etc. C.O.A.M.E.--Customer owned and maintained equipment. CODEC--The combination of a coder and decoder, as used in time-division switching systems to code the incoming message and decode the message being returned to the caller. It is a contraction of the words, coder and decoder. COMMON CONTROL--An exchange control method in which the dialed signals are received and registered separately from the switching elements before they are used to control these switches. Also defined as a control method, which identifies the input and output terminals of the switching network and then causes a connecting path to be established between them. Such systems are also designated as marker systems. CONCENTRATION STAGE--A switching stage in which a number of input lines are connected to a smaller number of output lines or trunks, as in the connection of a large number of subscriber lines to a smaller number of trunks based on the grade of service desired. CONGESTION FUNCTION--Any function used to relate the degree of congestion to the traffic intensity. CONNECTING ROW--All those crosspoints directly accessible from an inlet. Only one connection can be established via a connecting row at any instant. COUPLER--A device used to prevent electrical flashback and maintain normal electrical flow on a telephone line. Used as a buffer between C.O.A.M.E. and telephone company equipment. CROSSBAR SWITCH--A switch having a plurality of vertical paths, a plurality of horizontal paths and electromagnetically operated mechanical means for connecting any of the vertical paths with the horizontal paths. CROSSPOINT--A crosspoint comprises a set of contacts that operates together and extends the speech and signal wires of the desired connection. Each connection in a space-division switching network is established by closing one or more crosspoints. CROSSTALK--An unwanted transfer of signals from one circuit to another as may occur between switching elements or circuit wiring. C.W.A.--The Communication Workers of America. The C.W.A. reprsents 90 percent of the unionized Telco work force. DAY-TO-BUSY HOUR RATIO--The ratio of the 24 hour day traffic volume to the busy hour traffic volume. In some countries the reciprocal of this ratio is used. D.D.D.--Direct Distance Dialing. Also known as one-plus dialing. DELAY SYSTEM--A switching system in which a call attempt, which occurs when all accessible paths for the required connection are busy, is permitted to wait until a path becomes available. DIAL PULSE--The signaling pulse which is formed by the interruption of the current in the DC loop of a calling telephone. Such interruptions are produced by the breaking of the dial pulse contacts of the calling telephone subset during the dialing process. DIAMOND-RING TRANSLATOR--An array of ring-type induction coils associated with coded wiring in such a manner that the translation of directory numbers to equipment number or vice versa can be accomplished in an exchange. It is named after its originator, T.L.Dimond of the Bell Telephone Laboratories. DIRECT CONTROL--An exchange control method in which pulses, dialed by the subscribers, control directly the route selection switches of the system. For each digit dialed the equivalent of one set of selector switches is required with this control method. DIRECTOR--A control element which provides a measure of common control in step-by-step or Strowger exchanges. DISTRIBUTING FRAME--A structure for terminating the wires of a telephone exchange in such a manner that cross-connections can be made readily. Examples are the main distribution frame (MDF) at the entry of an exchange, intermediate distribution frames (IDF) between sections of an exchange, and power distribution frames (PDF). DISTRIBUTION STAGE--A switching stage between a concentration stage and outlets and serves as a means of selecting trunks to the desired terminations. DUV--Data Under Voice (AT&T System). ELECTROMECHANICAL SWITCHING SYSTEM--An exchange system in which both the speech paths and the control equipment are switched by electromechanical components--such as relays, rotary switches, etc. ELECTRONIC SWITCHING SYSTEM--An exchange system in which at least the control equipment is composed of electronic circuits and components, generally of a solid-state type. EMD SWITCH--The speech-path switching element used in a Siemens rotary switching system. EMD is an abbreviation of Edelmetall-Motor-Drehwahler, which translates in English to Noble-Metal Motor Switch. END OFFICE--A central office or Class 5 office. ENTRAIDE--A switching system in which outlets from a given connecting stage are connected to inlets of the same or a previous stage. In such systems calls may traverse a stage more than once. Usually these reentering links are used as last choice paths and the resulting network is heterogeneous. Such an arrangement is used in ITT's Pentaconta Crossbar system. ERLANG--The unit of traffic intensity, which is measured in call-seconds per second or call-minutes per minute. Also, one erlang equals 3600 call-seconds per hour. It is named after A. K. Erlang, the Danish engineer and mathematician who first adopted it. ESS--Electronic Switching System. EXCHANGE--All numbers within a given three-digit prefix area. Can also be used to describe a geographical area the size of a city. FX--Foreign Exchange Calls. The term applied to calls made to a central office other than the one located in the calling customer area. H.C. INSTRUMENT--An ordinary telephone with no extras. I.D.E.W.--International Brotherhood of Electrical Workers. A union that represents seven percent of all unionized telephoe workers. INTERSTATE--Telephone service that crosses state lines. Such services come under the jurisdiction of the F.C.C. INTRASTATE--Telephone services that remain within the boundares of a state. Such services come under the jurisdiction of the P.S.C. JOINT PRACTICES--An inter-company guide akin to the Geneva rules of war. The J.P. covers such things as intervals, offerings, and procedures. K.K.6--Six-button telephone. The standard telephone found in most offices. The K.K.6 can handle five lines. The sixth button is used for hold. LAYOUT CARD--Schematic drawings of the electrical circuits required for a telephone installation. LINK (TRUNK) The connection between the terminals of one switch and the terminals on a switch of the next stage corresponding to a single transmission path. LINK (ONE-WAY AND TWO-WAY)--A one-way link is used only for the establishment of connections in one direction, while a two-way link is used for the establishment of connections in either direction. LINK SYSTEM--A system in which: (1) there are at least two connecting stages; (2) a connection is made over one or more links; (3) the links are chosen in a single logical operation; and (4) links are seized only when they can be used in making a connection. LOGIC FUNCTION--The relationship of two or more Boolean variables as expressed by Boolean algebra. LOGIC GATES--Electrical or electronic circuits which control the transfer of signals and produce the required outputs for specific input combinations to implement Boolean logic functions. LOGIC (HARD-WIRED)--Control logic in an exchange, which is wired in circuit form. LOGIC (SOFT-WIRED)--Control logic in an exchange, which is held in software computer programs. LONG DISTANCE--Technically, any call that terminates more than seventeen miles from the source. LONG LINES--A division of AT&T responsible for the day-to-day operation of the long distance network. While the local Telco handles all maintenance, Long Lines directs overall supervision. LOOP DISCONNECT PULSING--Subset dial pulsing in which the subscriber DC loop is interrupted to produce pulses for signaling an exchange. MARKER--Circuits which incorporate the function of busy testing, locating and finally controlling the establishment of a particular path through the switching network. MARKETING REP--The sales people of the Bell companies. Also known as account executive. MARKING--The use of electrical potentials and grounds at certain points in a switching network to control its operation. MATRIX--A simple switching network in which a specified inlet (matrix row) has access to a specified outlet (matrix column) via a crosspoint placed at the intersection of the row and column in question. A complete matrix is one in which each inlet has access to each outlet, while an incomplete matrix is one in which each inlet may have access to only some of the outlets. MEAN DELAY OF CALLS DELAYED--The total waiting time of all calls divided by the number of delayed calls. MESSAGE SWITCHING--A method of receiving and storing a message for a more appropriate time of retransmission. With such a method, no direct connection is established between the incoming and outgoing lines as in the case of circuit switching. MULTIFREQUENCY SIGNALING--Signaling between subscribers and the central office through a combination of audio frequencies, as with pushbutton dialing. Also, in many cases signaling between exchanges is accomplished by combinations of frequencies. MULTIGROUP--A combination of two or more PCM multiplex channels. NONLISTED NUMBERS--Telephone numbers that do not appear in the directory but that are available if the inquirer calls directory assistance. NONPUBLISHED NUMBERS--Telephone numbers not made available to the public. Also known as silent numbers. OCCUPANCY--The average proportion of time that a traffic carrying facility is busy. PACKET SWITCHING--Essentially the same as message-switching. PANEL-SWITCHING SYSTEM--A common control electromechanical switching system, which was used widely in the U.S. prior to its virtual replacement by crossbar and other systems. The banks of selectors take the form of flat vertical panels, from which the name of the system was derived. Some panel installations are still in use in the U.S. PATH--A set of links joined in series to establish a connection. Paths differ if one or more links differ. P.B.X.--Private Branch Exchange. Commonly known as a switchboard. Mini-central office equipment for business customers with from 10 to 2,000 telephones. PRIMARY CENTER--A switching center connecting toll centers, which can also serve as a toll center for its local end offices. In the U.S. it is defined as a Class 3 office. PRIVATE AUTOMATIC BRANCH EXCHANGE (PABX)--A private automatic telephone exchange which provides for the connection of calls going to and coming from the public telephone network (usually a central office exchange) as well as intraexchange calls between the served extensions. PROBABILITY OF DELAY--The probability that a call attempt, if offered, cannot be completed immediately. PROBABILITY OF LOST CALLS (PROBABILITY OF LOSS)--The probability that a call attempt, if offered, will be lost. PROGRAM STORE--The memory section of a stored program control switching in which semi-permanent instructions and translations are contained. These are fed to the central processor to permit it to provide stored program control. PUBLIC SWITCHED NETWORK--Any switching system that provides circuit switching facilities for use by the public. Telephone, Telex, TWX, and Broadband switched networks are the public switched networks in the U.S. PULSE AMPLITUDE MODULATION (PAM)--A form of pulse modulation in which a number of channels are multiplexed by time sampling, but one in which the pulse amplitudes vary in accordance with the amplitude of the analog signal levels. PULSE CODE MODULATION (PCM)--A form of pulse modulation in which a number of channels are multiplexed by time sampling as in PAM, but with each amplitude replaced by a group of binary pulses which identify the amplitude of