Definitions and Terms Digital Telephone Switching System Part 8


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Some of the definitions and terms associated with Central Office (CO) digital telephone switching systems are defined below:

Definitions and Terms Digital Telephone Switching System Part 8

Tip Cable: A small (usually 100-pair) cable connecting terminals on a distributing frame to cable pairs in the cable vault.
Toll: The charge of making calls outside the boundaries of an exchange. Also a general term applied to the facilities and services of carriers used in conjunction with making toll (long distance) calls.
Toll Center: A switching center in the Bell System hierarchy of exchange classes. The toll center is a class four (4) exchange. It is used to connect end offices to long distance (toll) circuits. It can be used to establish connections with other central offices to increase routing options.
Traffic Carried: The amount of traffic carried (by a group of circuits or a group of switches) during any period is the sum of the holding times expressed in hours.
Traffic Flow: The traffic flow (on a group of circuits or a group of switches) equals the amount of traffic divided by the duration of the observation, provided that the period of observation and the holding times are expressed in the same time units. Traffic flow calculated in this way is expressed in erlangs.
Transhybrid Loss: The amount of isolation (in decibels) between go and return paths on the four-wire side of a four-wire to two-wire hubrid.
Transmission Level Point (TLP): A specification, in decibels, of the signal power at a point in a transmission system relative to the power of the same signal at a zero transmission level point (0 dB-TLP).
Transmission Reference Point (TLP): A hypothetical point used as the zero relative level point in the computation of nominal relative levels.
Transmultiplexer (Trunsmux): A type of equipment that transforms signals derived from frequency-division-multiplexed equipment (such as group or super-group) to time-division-division-multiplexed signals having the same structure as those derived from PCM multiplex equipment (such as primary or secondary PCM multiplex signals) and vice versa.
Trunk: A circuit or channel between two switching systems.
TST: Time-Space-Time digital switching structure.
Two-Wire Circuit: Is a circuit consisting of a single pair of wires and capable of simultaneously carrying two signals in opposite directions.

Two-Way Trunk: A trunk circuit that can be seized at either end of the circuit.
Unipolar: A binary line code using single polarity pulses and zero voltage for the two coding levels.
Virtual Call (Circuit): A user facility in which a call setup procedure and a call clearing procedure will determine a period of communication between two DTEs in which the user’s data will be transferred in the network in the packet mode of operation. All the user’s data are delivered from the network in the same order in which they are received by the network.
Voice Frequency Bandwidth: The human voice is capable of producing sound of various tones. In telephony, the normal voice frequency band is from 300 Hz to 3400 Hz.
Wait on “Busy”: A subscriber making a call to a busy number holds the call and is connected when the number is free.
Wide Area Telephone Service (WATS): For a flat-rate a subscribed area from a particular telephone termination is charged without the registration of call charges.
Waiting Time Jitter: Arrival time jitter in a digital signal produced by pulse stuffing operations and occurring because timing adjustments must wait for predefined time slots to occur.

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