Glossary A-Law. A companding characteristic used in European PCM systems. ABSBH. Average busy season busy hour. Adaptive Delta Modulation. Delta modulation using a step size that depends on the magnitude of the input. Adaptive Predictive Coding. Coding based on predicting the present input sample using the previous cycle or pitch period. Adaptive Pulse Code Modulation. Pulse code modulation using adaptive quantization. Adaptive Quantization. Quantization in which the step size varies so that it matches the variance of the input signal. Adaptive Transform Coding. A coding technique in which input subbands are trans- formed and the resulting coefficients encoded, usually using adaptive PCM. Address. (1) The destination of a message in a communications system. (2) The group of digits comprising a complete telephone number. Address Signals. Signals which are used to convey destination information. ADM. Adaptive delta modulation. ADPCM. Adaptive DPCM. Aliasing. A condition in which a frequency t::../ above half the sampling rate is repro- duced as a frequency t::../ below half the sampling rate. Alternate Routing. The use of a route other than a direct or first-choice route. Amplitude-Phase Keying (APK). Digital modulation in which both the amplitude and the phase of the carrier are altered to produce the various symbol states. ANSI. American National Standards Institute. APC. Adaptive predictive coding. APCM. Adaptive pulse code modulation. APD. Avalanche photodiode. A detector used in optical fiber systems. Array, Switching. A matrix of crosspoints forming part of a switching network. Asynchronous Communication. A mode of transmission characterized by start/stop operation with undefined time intervals between transmissions. ATC. Adaptive transform coding. Availability. The percentage of time during which a system provides its intended service. Average Busy Season Busy Hour. The three months with the highest average traffic in the busy hour, excluding Mother's Day, Christmas, and extremely high traffic days attributed to unusual events. b.e.r. Bit error rate. Block Code. A code in which the redundant bits relate only to the information bits of the same block. Blocking. The inability of a telecommunications system to establish a connection because of the unavailability of a path. 431
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Glossary
A-Law. A companding characteristic used in European PCM systems. ABSBH. Average busy season busy hour. Adaptive Delta Modulation. Delta modulation using a step size that depends on
the magnitude of the input. Adaptive Predictive Coding. Coding based on predicting the present input sample
using the previous cycle or pitch period. Adaptive Pulse Code Modulation. Pulse code modulation using adaptive quantization. Adaptive Quantization. Quantization in which the step size varies so that it matches
the variance of the input signal. Adaptive Transform Coding. A coding technique in which input subbands are trans
formed and the resulting coefficients encoded, usually using adaptive PCM. Address. (1) The destination of a message in a communications system. (2) The
group of digits comprising a complete telephone number. Address Signals. Signals which are used to convey destination information. ADM. Adaptive delta modulation. ADPCM. Adaptive DPCM. Aliasing. A condition in which a frequency t::../ above half the sampling rate is repro
duced as a frequency t::../ below half the sampling rate. Alternate Routing. The use of a route other than a direct or first-choice route. Amplitude-Phase Keying (APK). Digital modulation in which both the amplitude
and the phase of the carrier are altered to produce the various symbol states. ANSI. American National Standards Institute. APC. Adaptive predictive coding. APCM. Adaptive pulse code modulation. APD. Avalanche photodiode. A detector used in optical fiber systems. Array, Switching. A matrix of crosspoints forming part of a switching network. Asynchronous Communication. A mode of transmission characterized by start/stop
operation with undefined time intervals between transmissions. ATC. Adaptive transform coding. Availability. The percentage of time during which a system provides its intended
service. Average Busy Season Busy Hour. The three months with the highest average traffic
in the busy hour, excluding Mother's Day, Christmas, and extremely high traffic days attributed to unusual events.
b.e.r. Bit error rate. Block Code. A code in which the redundant bits relate only to the information bits
of the same block. Blocking. The inability of a telecommunications system to establish a connection
because of the unavailability of a path.
431
432 GLOSSARY
BORSCHT. An acronym referring to functions performed in, or in connection with, subscriber line circuits in a switching system: Battery, Overload protection, Ringing, Supervision, Coding, Hybrid, and Test access.
BPSK. Bi-phase shift keying. Break. The open state of relay or switch contacts. Bridged Tap. A pair of wires branched from a main pair in a telephone cable. BRZ. Bipolar return to zero. A channel code used for digital transmission. Busy Hour. The clock hour during which the most traffic is experienced in a switching
system or over a group of circuits. B3ZS. Bipolar with three-zero substitution. A channel code. B6ZS. Bipolar with six-zero substitution. A channel code. B8ZS. Bipolar with eight-zero substitution. A channel code. C-Message Weighting. A noise weighting used in a noise measuring set to measure
noise on a line that would be terminated by a device having acoustic properties similar to those of a Western Electric Type 500 telephone set.
Call Progress Signals. Signals sent to a caller by a switching system to provide informa-tion relative to the establishment of a connection.
CCIS. Common channel interoffice signaling. CCITT. International Consultative Committee for Telegraphy and Telephony. CDM. Continuous delta modulation. CDMA. Code-division multiple access. A technique involving spread spectrum trans
mission to provide a degree of protection against jamming. Central Office. One or more public network switching systems installed at a single
location; the term is often used synonomously with switching system. Cepstrum. The Fourier transform of the logarithm of the power spectrum. Channel Bank. A device which combines a number (e.g., 24) of voice channels together
into a digital stream (e.g., at 1.544 Mb/s) based upon sampling each voice channel at a specific rate (e.g., 8000 times per second).
Channel Coder. A device that processes a binary input into a multilevel or modified binary signal.
Characteristic Impedance. The impedance a transmission line would present at its input terminals if it were infinitely long.
Clock. Equipment providing a time base used in a transmission system to control the timing of certain functions such as the control of the duration of signal elements, and the sampling (CCITT).
Coding. Conversion of an analog function to digital form using a specific set of rules. Combined Switching. In time division switching, the switching of each direction of
conversation by a single control. Common Channel Interoffice Signaling (CCIS). A signaling system used in North
America, in which a separate signaling network is used to exchange supervisory and address signals between switching systems.
Common Equipment. Items of like equipment used on a shared basis by a switching system to establish connections.
Communications Quality. Speech quality which is acceptable to military, amateur and citizens band operators, often in a mobile environment.
GLOSSARY 433
Compandor. A compressor-expander. Compressor. A device which reduces the dynamic range of a signal. Concentration. The process of connecting any of a number of inlets to one of a
smaller number of outlets. Continuous Delta Modulation. Delta modulation using syllabic adaptation of the
step size. Continuously Variable Slope Delta Modulation. Delta modulation using a set of
discrete values of slope variations in which the slope changes are done at a syllabic rate.
Convolutional Code. A code in which the redundant bits check the information bits in previous blocks.
Correlation. Multiplication of an incoming signal by a locally generated function and averaging of the result. If the locally generated function is a delayed form of the received signal, the process may be called autocorrelation.
Correlative Coding. Coding which uses finite memory to change the baseband digital stream to a form which improves coding efficiency from a spectrum occupancy viewpoint.
Crosspoint. A controlled device used by a switching system to connect one path to another.
Crosstalk. Undesired power coupled to a communications circuit from other communi-cations circuits; may be intelligible or unintelligible.
CSU. Channel service unit. CVSD. Continuously variable slope delta modulation. CWR. Continuous word recognition. Data Under Voice (DUV). Transmission in which a digital stream is sent using base
band frequencies lower than those used for analog transmission. dBm. Power level in decibels referred to a power of one milliwatt, used in telephony
as a measure of absolute power. dBmO. The power in dBm measured at, or referred to, a point of zero transmission
level. dBrnc. Decibels above reference noise with the reference at -90 dBm using C-message
weighting. DCDM. Digitally controlled delta modulation. Delay. The amount of time by which a signal or event is retarded, expressed in
time or in number of symbols or characters. Delta Modulation. A one-bit version of DPCM in which the output bits convey
only the polarity of the difference signal. Demand Assignment. The assignment of a channel on demand when needed, for
the duration of the communication. Dial Pulsing. A means of address signaling consisting of regular, momentary interrup
tions of the direct current path at the sending end, in which the number of interruptions corresponds to the value of the address digit being transmitted.
Differential Pulse Code Modulation. Pulse code modulation in which the quantization is done on a differential waveform produced by subtracting from the input the previous value of the output, or a weighted combination of previous output values.
434 GLOSSARY
Digit Synchronization. The condition in which each digit (usually bit) is correctly sampled by the receiver, thus assuring its proper reception.
Digital. Information in the form of one of a discrete number of codes. Digital Radio. A radio that transmits a signal whose informational content is at
least partly digital. Digital Termination Systems (DTS). Radio local loops provided by competing common
carriers in a given metropolitan area. Digitally Controlled Delta Modulation. Delta modulation in which step size informa
tion is derived directly from the bit sequence produced by the sampling and quantization process, with companding at a syllabic rate.
Diphthong. A gliding monosyllabic speech item that starts at or near the articulatory position for one vowel and moves to or toward the position for another.
Dispersion. Pulse broadening in an optical fiber caused by multipath wave propagation. The result is intersymbol interference, corresponding to a limitation on the bandwidth that can be transmitted.
Distribution. The switching of traffic between concentration and expansion portions of a switching system network.
Dithering. A variation of the quantization levels to break up signal-dependent patterns in the quantized result.
Diversity. The use of dual frequencies, paths, or polarizations to minimize fading problems in a microwave radio relay system.
DLQ. Dynamic locking quantizer. DM. Delta modulation. DPCM. Differential pulse code modulation. Dry Contacts. Contacts through which no direct current flows. DSI. Digital speech interpolation. DSU. Data service unit. DTMF. Dual tone multifrequency signaling. Dual Tone Multifrequency Signaling. A method of transmitting address signals by
transmitting a pair of discrete tones from a group of eight tones, usually used on subscriber lines.
Duobinary. A correlative coding technique in which a two-level binary sequence is converted into one that uses three levels. The conversion involves intersymbol interference extending over one bit interval.
Dynamic Locking Quantizer. A quantizer capable of sensing and handling either speech or data inputs.
Dynamic Range. The difference between the overload level and the minimum acceptable signal level.
E & M Signaling. A technique for transferring information between a trunk circuit and a separate signaling circuit over leads designated E and M.
Echo. A reflection of a transmitted signal having sufficient magnitUde to be perceived as separate from the transmitted signal.
EIRP. Effective isotropically radiated power. Elastic Store. A digital store unit which accepts data under one timing source but
outputs it under another. In this manner, jitter related to either the input or the output can be removed.
GLOSSARY 435
Erlang. A unit of telephone traffic intensity obtained by multiplying the number of calls by the average length of calls in hours. One erlang equals 60 minutes.
Error Coder. A device which adds redundant bits to a bit stream to provide for error detection and possibly correction, at the receiver.
Expander. A device which increases the dynamic range of a signal. Expansion. The process of connecting any of a number of inlets to one of a larger
number of outlets. Extended Framing Format. An extension of the multiframe structure for use of the
framing bit sequence for signaling, cyclic redundancy check, and a data link. F-Bit. Framing bit. Fade Margin. The number of decibels by which a signal can fade before the fade
takes the signal's level below the receiver's threshold. Far-End Crosstalk (FEXTI. Crosstalk that is propagated in a disturbed channel in
the same direction as the propagation of signals in the disturbing channel. FDMA. Frequency-division multiple access. FEXT. Far-end crosstalk. Footprint. The coverage area on the surface of the earth from a satellite beam. Formant. A band of speech energy in the frequency spectrum. A resonance frequency
of the vocal tract tube. Four-Wire Circuit. A two-way transmission circuit using separate paths for each
direction of transmission. Frame Synchronization. The condition in which each frame or block of received
bits is correctly timed with respect to the received signal for the proper identification of the received bits as well as the individual channels.
Framing. The determination of which groups of bits constitute quantized levels and which quantized levels belong to which channels.
Fresnel Zone. A means of expressing the clearance of a microwave beam over an obstacle. The boundary of the nth Fresnel zone consists of all points from which the reflected wave is delayed n/2 wavelengths.
Fricative. A sustained unvoiced sound produced from the random sound pressure that results from turbulent air flow at a constricted point in the vocal system.
G/T. The ratio of a receiving system's gain to its noise temperature. Glare. The condition resulting from a near-simultaneous seizure of a two-way trunk
from both ends, in which the seizure signal appears to each switching system as a signal indicating a readiness to receive address digits.
Graded Index Fiber. An optical fiber which minimizes dispersion effects by providing nearly the same travel time for the various propagating modes.
Ground Start. A method of supervision on subscriber lines by which a seizure is indicated by placing ground potential on one of the conductors.
HDBH. High day busy hour. High Day Busy Hour. The hour in the one day, among the ten in the ten high
days, which has the highest traffic during the busy hour determined from the ten high day busy hour analysis.
Holding Time. The total time that a circuit is held busy, usually expressed in seconds. HP A. High powered amplifier. The output stage in a transmitting earth station for
satellite communication.
436 GLOSSARY
Hybrid Coder. A combination waveform and parametric coder. Often a hybrid coder will perform waveform coding of voice pitch but parametric coding of the voice formants.
IC. Integrated circuit. An electronic circuit that consists of many individual circuit elements such as transistors, diodes, resistors, capacitors, inductors, and other active and passive semiconductor devices, formed on a single chip of semiconducting material and mounted on a single piece of substrate material.
Impulse Function. A function that begins and ends within a time so short that it may be regarded mathematically as infinitesimal although the area described by the function remains finite.
Impulse Noise. Intermittent or spasmodic noise consisting of high-level pulses of short duration.
Index of Refraction. The ratio of the velocity of light in vacuum to the velocity of light in a given medium (e.g., an optical fiber).
Integrated Services Digital Network. A switched network, with end-to-end digital connectivity, which supports a wide range of services.
Interdigital Time. The time interval between address digits being transmitted over a circuit.
Interface. The point at which two systems or two parts of one system interconnect. IRED. Infrared emitting diode. A source used in optical fiber systems. ISDN. Integrated services digital network. IWR. Isolated word recognition. Jitter. Short term variations of the significant instants of a digital signal from their
ideal positions in time (CCITT). Laser Diode. A junction diode consisting of positive and negative carrier regions
with a P-N transition region (junction) that emits electromagnetic radiation at optical frequencies. The emitted beam is very narrow, allowing the output to be coupled efficiently into single mode fibers usable in long range optical transmission systems.
LDM. Linear delta modulation. LED. Light-emitting diode. A source used in short range optical fiber systems. A
diode that emits electromagnetic radiation at optical frequencies. The emitted beam is broad, allowing the output to be coupled efficiently only into relatively large cross-section multimode fibers. Such fibers normally are used only in short-range optical transmission systems.
Linear Delta Modulation. Delta modulation in which the input time function is approximated by a series of linear segments of constant slope.
Linear Predictive Coding. A parametric coding technique in which the perceptually significant features of speech are extracted from its waveform.
LNA. Low noise amplifier. The input stage of a receiving earth station for satellite communication. Its effective noise temperature usually is lower than the ambient temperature.
Logarithmic Compression. Reduction of the dynamic range of a signal based upon the logarithm of its instantaneous amplitude.
Long Haul. Transmission over a microwave radio relay system to distances in excess of 400 km.
GLOSSARY 437
Loop Start. A method of supervision on subscriber lines by which a seizure is indicated by a closure of the two conductors in the subscriber loop.
Loss. (1) Power that is dissipated in a circuit without doing useful work. (2) The drop in power of a signal traversing a circuit or a switched connection.
LPC. Linear predictive coding. LSI. Large-scale integration of circuitry in semiconductor elements. MF. Multifrequency signaling. ,...-Law. A companding characteristic used in North American PCM systems. Make. The closed state of relay or switch contacts. Metropolitan Area Trunk (MAT). A cable designed to minimize crosstalk where
large numbers of circuits are required between central offices. Modem. A modulator-demodulator. This device is used to convert a digital stream
to a quasi-analog form (tones) suitable for transmission on analog facilities, and to reconvert to digital form at the receiving end.
Modified Duobinary. A correlative coding technique in which the intersymbol interference extends over two bit intervals.
Modulation. Variation of the amplitude, frequency, or phase of a carrier wave to convey information.
MSK. Minimum shift keying. A form of frequency shift keying in which the peak frequency deviation equals ± 0.25 times the bit rate and coherent detection is used.
Muldem. A multiplexer-demultiplexer. Multiframe. A set of twelve consecutive frames in which the position of each frame
can be identified by reference to a multiframe alignment signal for the group of consecutive frames.
Multifrequency Signaling (MF). A signaling system, normally used on telephone trunks, by which address digits are indicated by a pair of discrete tones.
Multimode Fiber. An optical fiber whose diameter is large enough to allow the transmission of multiple propagation modes.
Multiple Access. Techniques allowing variously located earth terminals to use portions of a satellite's transponder on either a frequency- or a code- or a time-division basis.
Near-End Crosstalk (Next). Crosstalk that is propagated in a disturbed channel in the direction opposite to the propagation of signals in the disturbing channel.
Noise. Any unwanted signal or interference on a circuit other than the signal being transmitted.
Noise Figure. The ratio, expressed. in decibels, of a system's input signal-to-noise ratio to its output signal-to-noise ratio.
Nonblocking. The ability of a telecommunications system to establish a connection from an inlet to an outlet irrespective of the amount of traffic.
NRZ. Nonretum to zero. A channel code, in which there are only two states of a signal parameter used to represent data. These are the 0 state and the 1 state.
Off Hook. (1) In line signaling, the condition indicating that a line is in use (line loop: closed). (2) In trunk signaling, the signaling state which exists, in the forward direction, to indicate a seizure of the trunk by the switching equipment, and in
438 GLOSSARY
the backward direction, to indicate an answered call or an element of signaling protocol.
On Hook. (I) In line signaling, the condition indicating that a line is idle (line loop: open). (2) In trunk signaling, the signaling state which exists, in the forward direction, to indicate that the trunk is not in use and, in the backward direction, to indicate that a call is awaiting an answer, a disconnect signal from the called end, or an element of signaling protocol.
Outpulsing. The transmission of address digits necessary to establish a switched connection.
Packet Transmission. The transmission of a stream of bits which has been divided into packets of a specific length (e.g., 1024 bits). Each packet carries its address. The overall stream is reassembled at the receiving location.
Pad. A resistance or other network inserted into a transmission path to provide a controlled amount of loss in the path.
Parametric Coder. A device which is designed to digitize an input in terms of its parameters, such as frequency bands, amplitudes, periodicities, etc.
Parity Bit. The name given to a redundant bit added to a sequence of information bits so the total sequence adds to either one or zero. If the received sequence does not add to the same number (one or zero), a parity error is said to have occurred.
Partial Response Signaling (PRS). The use of controlled intersymbol interference to increase the transmission rate in a given bandwidth.
PCM. Pulse code modulation. Peg Count. The count of the number of traffic attempts made on a group of circuits
or equipment elements during a given time period. Phase Shift Keying. A form of digital modulation in which the bits shift the instantane
ous phase between predetermined discrete values. It uses 2 m phases to represent m bits of information each.
Phoneme. A distinctive sound within a language. Pitch. The fundamental or lowest predominant frequency produced by the human
voice. Plosive. A sound resulting from making a complete closure (usually toward the mouth
end), building up pressure behind the closure, and abruptly releasing it. The letters B, K, P and Tare plosives.
Polarization. The direction of the electric vector of a propagating electromagnetic wave. For circular polarization, this vector rotates at a rate equal to the carrier frequency.
Polybinary. A correlative coding technique in which the intersymbol interference extends over more than two bit intervals.
Prediction. The process of estimating a future value by using weighted sums of past values.
Private Automatic Branch Exchange (P ABX). An automatic switching system providing switched telephone communications at a subscriber's premises and connections between the premises and the public switched network.
Protection Channel. A spare channel for use when channel equipment outages occur, or during deep fades on a microwave radio relay system.
GLOSSARY 439
Pseudonoise Generator. A generator of a very long periodic digital sequence. The length of the stream is great enough that it appears to be random.
Psophometric Weighting. Selective attenuation of voiceband characteristics based upon the use of a filter recommended by the CCITT and calibrated with an 800 Hz tone at 0 dBm.
Pulse Code Modulation. The use of a code to represent quantized values of instantaneous samples of a waveform.
Pulsing. The generation and transmission of pulses to provide signaling information to a switching system.
QAM. Quadrature amplitude modulation. QPRS. Quadrature partial response signaling. QPSK. Quaternary phase shift keying. Quadrature Amplitude Modulation. The independent amplitude modulation of two
orthogonal channels using the same carrier frequency. Quantization Noise. Noise produced by the error of approximation in the quantization
process. Real Time. Pertaining to the actual time during which a physical process transpires. Regeneration. The process of recognizing and reconstructing a digital signal so that
the amplitude, waveform, and timing are constrained within stated limits (CCITT). Reliability. The percentage of time during which equipment performs its intended
function. Retrial. An additional attempt to seize a unit of equipment or a circuit, or to find
a path through a switching network, after a previous attempt has failed. Ring. One conductor in a pair of wires, distinguished from the tip conductor. Ringing Signal. A signal sent over a called line or trunk to alert the called party
by audible or visual means to the incoming call. Sampling. The process of sensing a waveform's amplitude at specific instants of time.
Sampling usually is done periodically. SBC. Subband coding. SCPC. Single channel per carrier. A technique used in thin-route satellite communica
tions. Scrambler. A device which alters a bit stream using a specific set of rules so that
the transmitted stream does not contain long sequences of zeros, but so that the receiver can reconstruct the original stream.
Sender. A device in an electromechanical common control switching system which receives address or routing information and outpulses the correct digits to a trunk or to the local equipment.
Separated Switching. In time division switching, the switching of each direction of conversation by separate controls.
Server. A circuit or item of equipment which provides service to a call attempt. Service Circuit. Any of several groups of common equipment used on a shared basis
within a switching system to establish connections. Short Haul. Transmission over a microwave radio relay system to distances less
than 400 km. Sidetone. The signal produced in a telephone receiver by one's own voice or by
room noise through the telephone transmitter.
440 GLOSSARY
Signaling. The transmission of address and other switching information between subscribers and switching systems or between switching systems.
Single Frequency (SF) Signaling. A method for conveying dial pulse and supervisory signals from one end of a trunk to the other end by the presence or absence of a single specified frequency.
Single-Mode Fiber. An optical fiber whose diameter is so small that only a single mode can propagate through it.
SNR. Signal-to-quantizing-noise ratio. Source Coding. The process of digitizing an analog input using a specific algorithm. SPADE. Single-channel per carrier Pulse code modulation multiple Access Demand
assigned Equipment. A SCPC technique used in thin route satellite communication. SPEC. Speech predictive encoded communications. Stop. A sound produced by an abrupt release of a pressure built up behind a complete
occlusion. STS. Space-Time-Space switching architecture. Subband Coding. Frequency-domain coding in which each of several subbands is
coded separately. Subrate. A digital rate less than 64 kb/s. Supervision. The process of detecting a change of state between busy and idle condi-
tions on a circuit. Switcher. A switching system. Switching Array. A matrix of crosspoints forming part of a switching network. Sync Character. A repetitive bit pattern used by a receiver to establish that synchroni-
zation has been achieved. Synchronization. A means of insuring that both transmitting and receiving stations
are operating together (in phase). Synchronous Communication. A mode of digital transmission in which discrete signal
elements (symbols) are sent at a fixed and continuous rate. Synthetic Quality. The quality of computer-generated speech, which often lacks hu
man naturalness. Synthetic quality speech is intelligible, but the speaker may not be recognizable.
Tandem. (1) A network arrangement in which a trunk from the calling office is connected to a trunk to the called office through an intermediate point called a tandem switching office. (2) To establish a trunk-to-trunk connection through a switching office.
TASI. Time-assignment speech interpolation. TCM. Time compression multiplexing. Time-domain separation of two directions
of transmission. TDM. Time division multiplexing. TDMA. Time-division multiple access. Ten High Day Busy Hour. The ten-day average traffic level for the time-consistent
busy hour, excluding Mother's Day, Christmas, and extremely high traffic days attributed to unusual events.
THDBH. Ten high day busy hour. Time Division Multiplexing. The sharing of a transmission circuit among multiple
GLOSSARY 441
users by assigning time slots to individual users during which anyone of them has the entire circuit's bandwidth.
Time Slot Interchange. A switching system element which switches between circuits by separating signals in time.
Tip. One conductor in a pair of wires used in telephony, distinguished from the ring conductor.
Toll Quality. Speech quality based upon a laboratory test in which the signal-tonoise ratio exceeds 30 dB and the harmonic distortion is less than 2%. The bandwidth is 300-3200 Hz.
Traffic. (1) The messages sent and received over one or a group of communication channels. (2) A quantitive measure of the total messages and their length, expressed in specified units.
Transient. A rapid fluctuation of voltage or current in a circuit, usually of short duration, caused by switching, changes in load, momentary crosses, ground, or by lightning surges.
Transmission Level. The power measured at a given point in circuit, usually expressed in dBm, over a given range of frequencies or at a specific frequency.
Transmission Level Point (TLP). The reference level point in a transmission system at which signal strength comparisons are made
Transmultiplexer. A device used to convert TOM signals to FOM, and vice versa, thus serving as an interface device between digital and analog networks.
Trunk. A communication channel provided as a common traffic path between two switching systems.
Trunk Circuit. A network of circuit elements used to connect a switching system to one of its associated trunks.
TSI. Time slot interchange. TST. Time-space-time switching architecture. Usage. The intensity of traffic carried by a group of circuits. VLSI. Very large-scale integration of circuitry in semiconductor elements. Vocoder. A device which is designed to digitize voice in terms of its pitch, amplitude,
voicing and formants. Waveform Coder. A device which converts samples of an analog waveform to bits. Wavelength-Division Multiplexing (WDM). The simultaneous transmission of optical
carriers of different wavelengths on a given optical fiber. Wink. A single supervisory pulse used between switching systems to signal a readiness
to receive address digits.
Index
Absorption, 168 Access tandem (AT), 391, 393-395 Action point (ACP), 370 Adaptive delta modulation (ADM), 54-58, 73-
299, 338, 347, 348, 353, 359 Concentrator, 158, 295, 411 Congestion, 326-329, 331 Consortium of European Postal and Telegraph
Organizations (CEPT), 148, 153, 188 Constellation, 123, 132-134 Consultative Committee International for Te
lephony and Telegraphy (CCITT), 148, 153,378,385,400,405,411,415,421, 423,426
Control manual, 248 progressive, 249 stored program, 246, 252, 290
Control architectures, 311-315
Control Complex, 248 Control concepts, 246, 311-315 Control functions, 247, 312 Control memory, 286, 287, 300, 331, 340, 344,
346, 359 Control subsystem, satellite, 212-213 Control switching point (CSP), 366 Controls, traffic, 328 Convolutional coding, 91 Cordless end instruments, 109-110 Correlation function, 43-44 Correlative techniques, 137-141 Coupling loss, source to fiber, 232, 235 Crossbar, 283, 284 Crosspoints, 246, 279-285, 295, 296, 347, 358 Crosstalk, 221, 372, 404
far-end, 110 near-end, 105, 110, 149, 404
Dark current, 236 Data above video, 161 Data above voice, 161 Data link layer, 405, 406 Data service unit (DSU), 73, 96-97 Data under voice (DUV), 139, 159-161, 180 DA TALINK service, 424 Datran, 425 Decimation, 154 Decode level, 378-381 Deferrable work time, 312 Delay dial, 268, 348 Delay distortion, 372, 375 Delta coding, 49-59, 73-75 Delta modulation (DM), 49-59, 73-75, 158,
Depolarization, rain, 193-195 Deutsche Bundespost, 417,418,420
INDEX 445
Deviation ratio, 137 Dial pulse signaling, 261-263, 369, 391, 392 Dial tone, 247, 251, 321 Digit receivers, 248, 321, 322, 326 Digital access and crossconnect system
(DACS),385 Digital conferencing, 307, 308 Digital data network (DDX), 408, 411 Digital electronic message service, 187-188 Digital filters, 307 Digital hierarchy, 96-97 Digital interface, 334, 338, 346, 361, 362, 380,
414 Digital milliwatt, 306, 378, 379, 382 Digital office timing supply (DOTS), 385, 424 Digital pads, 310, 331 Digital radio, 181-185 Digital speech interpolation (DSI), 102-104,
206,229 Digital stream rates, 147, 151 Digital switching systems, 293-330, 380, 382-
385,387,408,411,416,417,421,422 Digital symmetrical matrices, 305 Digital termination systems, 187-188 Digital transmission system
Signal transfer point (STP), 370, 371 Signals, call progress, 248, 271 Single channel per burst, (SCPB), 206 Single channel per carrier (SCPC), 197,201-
203 Single-frequency (SF) signaling, 257, 369 Single sideband, 141, 154, 192 SL Undersea Lightguide System, 228-229 Slip, 383-385, 414 Solar array, 206-207 Space division switching, 246, 300-305, 339,