Appendix B. Glossary - IBM 3872 User Manual

Attenuate: To lessen the amount, force, or value of.
Batch Processing: A system of accumulating and grouping a random
number of input items to be processed at one time.
Carrier: An oscillation or wave suitable for modulation by the
intelligence to be transmitted over the communications system.
Communications Channel: A single or dual transmission path, char-
acterized by a particular frequency bandwidth (voice bandwidth in
this manual).
Control Station: On a centralized multipoint communications
channel, the station responsible for control of message traffic on
that channel.
Conversation Mode: Communication between a terminal and a
computer, in which each entry from the terminal elicits a response
from the computer, and vice versa.
Data Communications: The transmission and reception of informa-
tion by data processing equipment, or communications terminal
equipment.
Data System: An organized collection of methods and interconnected
machines that accepts input data, processes the data, and provides
output data.
Dedicated Line: A communications channel which is permanently
connected between two or more data stations. (Also called "leased"
or "private".)
Delay (group): The time of propagation between two locations of a
certain point of the envelope of a wave (varies with the frequency).
Demodulation: The process of retrieving intelligence from a modu-
lated carrier wave.
Deserialize: To change from serial-by-bit to parallel-by-bit.
Distortion: The unwanted change in waveform that may occur be-
tween two points in a transmission system.
Duplex Facilities: A dual voiceband channel with complete separation
of transmit and receive at any station in a system. Any system which
uses the same portion or portions of the voiceband spectrum for
simultaneous transmission of signals in both directions requires duplex
facilities. To reduce turnaround time, carrier can be transmitted
continuously from both stations of a point-to-point system or from
the control station for a centralized multipoint system. Four-wire
duplex facilities avoid false startups caused by interference between
multipoint tributary stations.
Duplex Operation: A simultaneous two-way transmission.
Echo: A wave that is returned to the point of origin, because of re-
flection or some other cause.
Echo Suppressor: A line device used to prevent energy being reflected
back to the transmitter.
Equalizer: Any combination of active and/or passive elements inserted
in a transmission line or amplifier circuit to improve its frequency re-
sponse or phase characteristics.
Half Duplex Facilities: A single voiceband channel for bidirectional,
non-simultaneous transmission between any two stations in a system.
Systems that do not require use of the same portion or portions of
the voiceband spectrum for simultaneous transmission of signals in
both directions can operate with half-duplex facilities; carrier can be
transmitted in only one direction at a time.
Appendix B. Glossary
Note: When the common carrier supplies four-wire duplex
facilities for half-duplex mode of operation in a point-to-point
system, carrier may be maintained from both stations.
Half Duplex Operation: A two-way transmission of signals, but in
only one direction at a time.
Interface: A point of demarkation that divides the responsibilities of
any two connected pieces of equipment.
Leased, or Private, Line: See "dedicated line".
Mark: The quiescent or binary 1 data bit condition.
Modem: A contraction of "modulator-demodulator". This term may
be used when the modulator and demodulator are associated in the
same signal conversion equipment.
Modulation: A process by which certain characteristics of a wave are
modified in accordance with a characteristic of another wave or signal.
Noise: Any unwanted disturbance within a useful frequency band,
such as undesired electric waves in a transmission channel or device.
Off Hook: On-Hook: Activated/deactivated, in reference to a tele-
phone set; it may also be used in reference to a device attached to a
switched network line.
Parallel Data: Multiple signal elements, usually a character or byte,
transferred simultaneously.
Propagation Time (delay): The time necessary for a signal to travel
from one point of a circuit to another.
Serial Transmission: Transmission, at successive intervals, of signal
elements (not transmitted simultaneously).
Serialize: To change from parallel-by-bit to serial-by-bit.
Service: The common-carrier function of providing and maintaining
a system of facilities to meet customer communications requirements.
Space: The binary 0 data bit condition.
Station: An input or output point in a communications system.
Strap, Strapping: Selectable wiring to provide optional variations in
the performance of equipment.
Switched Line (switched network): A communications channel
made up of a number of shorter communications circuits connected
through switching facilities provided by a common carrier.
Teleprocessing: A form of information handling in which a data
processing system uses communications facilities.
Transmit Level: A power level of energy introduced onto the
communications channel by the transmitter.
Tributary Station: On a centralized multipoint communications
channel, one of two or more stations that transmits to, and receives
from, the control station.
Turnaround: The time required to reverse the direction of trans-
mission from send to receive, or vice versa. Time is required for line
propagations and line effects, reversal of echo suppressors (where
used), modem timing, and DTE reaction.
Two-wire or Four-wire: These terms refer to the physical connection
to the communications channel. They do not determine half-duplex
and duplex communications facilities.
Appendix B. Glossary B-1