Specifications

December 2008 Page C–1
Appendix C — Glossary
A-D Converter A device that converts an input
analog signal to an output digital signal with the
same information content.
a-law The PCM coding and companding
algorithm used in CCITT standard countries.
Acceptance angle The maximum angle,
measured from the longitudinal axis or centerline
of an optical fiber to an incident ray, within which
a ray will be accepted for transmission along the
fiber.
Address Anumerical expression that identifies a
location.
AIS Alarm Indication Signal.
Alarm A signal generated when abnormal
network conditions exist.
Major Alarm — Indicates major abnormal condi-
tions where a chassis is disrupted or out of service.
Minor Alarm — Indicates minor abnormal condi-
tions where a channel is out of service.
Alternate Path System is “Mapped” in opposite
direction around loop. It is the same origin and
destination, but a different path than the primary.
Alternate Mark Inversion (AMI) A bipolar
coding scheme in which successive ones must
alternate in polarity (positive and negative) but are
equal in amplitude and in which spaces or marks
are of zero amplitude. Synonymous with bipolar
signal.
American National Standard Code for
Information Interchange (ASCII) Used for data
processing and data communications to encode
keyboard and printer data.
Asynchronous Data A transmission method in
which each character or block of information is
individually synchronized, usually by the use of
start and stop elements, or bits.
Attenuation The decrease in power of a signal,
light beam, or lightwave, either absolutely or as a
fraction of the reference value.
Bandwidth Arange of frequencies between two
defined limits expressed in cycles per second or
Hertz (Hz). Also the information carrying capacity
of a circuit.
Baud The basic unit of modulation rate or
signaling speed.
Bipolar The predominant signaling method used
for digital transmission services in which binary
ones are represented by alternating positive and
negative pulses and binary zeros remain at zero
amplitude.
Bipolar Violation A bipolar pulse with the same
polarity as the preceding pulse. This is a violation
of the Alternate Mark Inversion rule.
Bit A unit of measure of information designated
by a specific value (e.g., binary digit ‘0’ or ‘l ‘).
Bit Rate The speed at which the bits are trans-
mitted (e.g., 2400 bps).
Bits per second A measure of speed in serial
transmission (e.g., Kbps for thousands of bits per
second, Mbps for millions of bits per second).
Block 1. A group of bits transmitted as a unit. 2. A
mode where PRI modules is not communicating
to the other end.
Bus One or more connectors that serve as a
common connector for a related group of devices.
Bypass The process by which a connection passes
through intermediate terminals between the call
origin point and the destination point.
Carrier A continuous frequency capable of being
modulated with a second (information carrying)
signal.
Central Office A facility where communications
common carriers (e.g., telephone companies)
terminate customer lines and locate switching
equipment that interconnects customers lines.
Also referred to as the CO, exchange, end office,
Appendix C – Glossary