Glossary
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
Digital Service, level 1 (DS1): The 1.544M bps voice standard (derived from an older Bell System standard) for digitized voice transmission in North America. The 1.544M bps consists of 24
Digital Signal: A discrete or discontinuous signal (e.g., a sequence of voltage pulses). Digital devices, such as terminals and comput- ers, 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 64K bps (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 anygiven 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
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
E
E&M: A telephony trunking system used for either
EIA: The Electronics Industries Association is a trade organization in Washington, DC that sets standard for use of its member companies. (See
Encapsulation: A technique used by
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
Ethernet: A
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.
Exchange Area: A geographical area with a single uniform set of charges (tariffs), approved by a regulatory group, for telephone services. Calls between any two points within an exchange area are local calls. See also "Digital PBX", "PBX".
Exchange Termination (ET): The carrier's local exchange switch. Contrast with "Loop Termination - LT".
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