Multitech MultiVOIP 800 MVP800 User's Guide download pdf (Page 99)

Glossary

Device driver: Software that controls how a computer communicates with a device, such as a printer or mouse.

Digital Cross-connect System (DCS): The CO device which splits and redistributes the T1 bandwidth. the DCS takes time slots from

various T1 lines and alters them to provide the needed connectivity. DCS connections are made with software at an administrator's

workstation.

Digital Data: Information represented by discrete values or conditions (contrast "Analog Data").

Digital Loopback: A technique used for testing the circuitry of a communications device. Can be initiated locally, or remotely (via a

telecommunications device). The tested device decodes and encodes a received test message, then echoes the message back. The results

are compared with the original message to determine if corruption occurred en route.

Digital PBX: A Private Branch Exchange that operates internally on digital signals. See also "Exchange".

Digital Service, level 0 (DS0): The world-wide standard speed (64 Kbps) for digital voice conversation using PCM (pulse coded

modulation).

Digital Service, level 1 (DS1): The 1.544 Mbps voice standard (derived from an older Bell System standard) for digitized voice transmission

in North America. The 1.544 Mbps consists of 24 digitally-encoded 64 Kbps voice channels (north America) and 2.048 Mbps (30 channels)

elsewhere.

Digital Signal: A discrete or discontinuous signal (e.g., a sequence of voltage pulses). Digital devices, such as terminals and computers,

transmit data as a series of electrical pulses which have discrete jumps rather than gradual changes.

Digital Signaling Rates (DSn): A hierarchical system for transmission rates, where "DS0" is 64 Kbps (equivalent to ISDN B channel), and

DS1 is 1.5 Mbps (equivalent to ISDN PRI).

Digital Transmission: A method of electronic information transmission common between computers and other digital devices. Analog

signals are waveforms: a combination of many possible voltages. A computer's digital signal may be only "high" or "low" at any given time.

Therefore, digital signals may be "cleaned up" (noise and distortion removed) and amplified during transmission.

Digitize: To convert an analog signal to a digital signal.

DIP switch (pronounced "dip switch"): A set of tiny toggle switches, built into a DIP (dual in-line package), used for setting configurable

parameters on a PCB (printed circuit board).

Driver: A software module that interfaces between the Operating System and a specific hardware device (i.e. color monitors, printers, hard

disks, etc.). Also known as a device driver.

Drop and Insert: The process where a portion of information carried in a transmission system is demodulated ("Dropped") at an

intermediate point and different information is included ("Inserted") for subsequent transmission.

DTE (Data Terminating Equipment): A term used to include any device in a network which generates, stores or displays user information.

DTE is a telecommunications term which usually refers to PCs, terminals, printers, etc.

DTMF (Dual-Tone MultiFrequency): A generic push-button concept made popular by AT&T TouchTone.

E&M: A telephony trunking system used for either switch-to-switch, or switch-to-network, or computer/telephone system-to-switch

connection.

EIA: The Electronics Industries Association is a trade organization in Washington, DC that sets standard for use of its member companies.

(See RS-232, RS-422, RS530.)

Encapsulation: A technique used by network-layer protocols in which a layer adds header information to the protocol data unit from the

preceding layer. Also used in "enveloping" one protocol inside another for transmission. For example, IP inside IPX.

Endpoint: The clients in an H.323 network. They are typically video conferencing, audio conferencing, or other multimedia systems

implemented by end users to communicate in real time. The H.323 standard requires that every endpoint support certain functions and

codecs (Coder/Decoder) that have previously been defined by the ITU.

Errored Seconds (ES): Any second of operation that all 1.544M bits are not received exactly as transmitted. Contrast "Error Free Seconds".

Error Free Seconds (EFS): Any second of operation that all 1.544M bits are received exactly as transmitted. Contrast "Errored Seconds".

ESF Error Event: A T1 error condition that is logged when a CRC-6 error or an OOF error occurs.

Ethernet: A 10-megabit baseband local area network that allows multiple stations to access the transmission medium at will without prior

coordination, avoids contention by using carrier sense and deference, and resolves contention by using collision detection and transmission.

Ethernet uses carrier sense multiple access with collision detection (CSMA/CD).

Excess Zeros: A T1 error condition that is logged when more than 15 consecutive 0s or less than one 1 bit in 16 bits occurs.

Exchange: A unit (public or private) that can consist of one or more central offices established to serve a specified area. An exchange

typically has a single rate of charges (tariffs) that has previously been approved by a regulatory group.

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Multitech MultiVOIP 800 MVP800 User's Guide Page 99

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