Specifications

Carrier
A continuous signal at a fixed frequency that is capable of being
modulated with a second (information carrying) signal.
Cell
The 53-byte basic information unit within an ATM network. The
user traffic is segmented into cells at the source and reassembled
at the destination. An ATM cell consists of a 5-byte ATM header
and a 48-byte ATM payload, which contains the user data.
Channel
A path for electrical transmission between two or more points.
Also called a link, line, circuit or facility.
Clock
A term for the source(s) of timing signals used in synchronous
transmission.
Control Signals
Signals passing between one part of a communications system
and another (such as RTS, DTR, or DCD), as part of a mechanism
for controlling the system.
CPE (Customer Premises
Equipment)
Generally refers to communications equipment located at the
customers' premises for use with communication service providers'
services. In some cases, these are customer-owned or leased; in
other cases, these are the property of the service provider.
CRC (Cyclic Redundancy
Check)
A data transmission error-detection scheme. A polynomial
algorithm is performed on the data, and the resultant checksum is
appended at the end of the frame. The receiving equipment
performs a similar algorithm.
Current Loop
Method of data transmission. A mark (binary “1”) is represented
by current on the line, and a space (binary “0”) is represented by
the absence of current.
Data
Information represented in digital form, including voice, text,
facsimile and video.
Data Link Layer
Layer 2 of the OSI model. The entity, which establishes, maintains,
and releases data-link connections between elements in a
network. Layer 2 is concerned with the transmission of units of
information, or frames, and associated error checking.
dBm
A measure of power in communications: the decibel in reference
to one milliwatt (0 dBm = 1 milliwatt and -30 dBm = .001
milliwatt).
Decibel
See dB.
Diagnostics
The detection and isolation of a malfunction or mistake in a
communications device, network or system.
Digital
The binary (“1” or “0”) output of a computer or terminal. In data
communications, an alternating, non-continuous (pulsating) signal.
Digital Loopback
A technique for testing the digital processing of a communications
device. The loopback is toward the line side of a modem, but tests
most of the circuitry in the modem under test.