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132 APPENDIX : GLOSSARY
DRAM Dynamic Random Access Memory—The readable/writable memory used to store
data in PCs. DRAM stores each bit of information in a "cell" composed of a
capacitor and a transistor.
DRJ Disengage Reject—This is a call flow message.
DRQ Disengage Request—This is a call flow message.
DS Digital Signal—Standard specifying the electrical characteristics for data
transmission over four-wire telco circuits. DS1 is 1.544 Mbps, and DS3 is 44.736
Mbps. Also referred to as T1 and T3.
DS0 1. Digital Signal level zero—It is equivalent to one voice conversation digitized
under PCM. It transmits digital signals over a single channel at 64-kbps on a T1
facility 2. Data Slot 0
DSP Digital Signaling Processors—A special computer chip designed to process digital
signals that were originally analog signals.
DSR Data Set Ready—This is a call flow message.
DTE Data Terminal Equipment—End-user equipment, typically a terminal or computer,
that can function as the source or destination point of communication on the
network.
DTMF Dual Tone Multi-frequency—The sounds a touch-tone telephone makes when its
keys are pressed.
DTR Data Terminal Ready—A control signal that is activated to let the DCE know when
the DTE is ready to send and receive data.
DTS Data Transformation Service—Technology designed for bypassing functions for
short-hop, line-of-sight applications. It never converts to analog. Its main use is in
high volume, data only applications in urban areas where line costs are higher.
ECC Error Correcting Code—Code that determines whether line noise has caused data
to be garbled or dropped in transit, and then works to correct the problem. The
two most common error-correction protocols and standards used by analog
modems are MNP and V.42.
EdgeServer Pro Card This card on the Total Control Chassis runs Windows NT 4.0 Server, provides two
10/100-Mbps ethernet interfaces, and routes call over IP networks.
Edge server card This card on the Total Control Chassis runs Windows 2000 Server, provides two
10/100-Mbps ethernet interfaces, and routes call over IP networks.
EDO RAM Extended Data Out Random Access Memory—A more efficient method to access
memory. It reduces access memory time by 10% over the standard DRAM chips.
EIA Electronic Industries Alliance—A trade organization who sets standards for
electronics.
EMC Electromagnetic Compatibility—The ability of a device or system to function
without error in its intended electromagnetic environment.
EMI Electromagnetic Interference—The leakage of radiation from equipment.