Glossary
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
Downstream: The direction of data flow from the host or away from the host. A downstream port is the port on a hub electrically farthest from the host that generates downstream data traffic from the hub. Downstream ports receive upstream data traffic.
Driver: When referring to hardware, an I/O pad that drives an external load. When referring to software, a program responsible for interfacing to a hardware device; that is, 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 Terminal 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
DWORD: Double word. A data element that is 2 words, 4 bytes, or 32 bits in size.
Dynamic Insertion and Removal: the ability to attach and remove devices while the host is in operation.
E
E&M: A telephony trunking system used for either
EIA: The Electronics Industries Association is a trade organization in Washington, DC that sets standards for use of its member companies. (See
Encapsulation: A technique used by
End User: The user of a host.
Endpoint: See Device Endpoint.
Endpoint Address: The combination of a Device Address and an Endpoint Number on a Universal Serial Bus device.
Endpoint Number: A unique pipe endpoint on a Universal Serial Bus device.
Ethernet: A
Excess Zeros: A T1 error condition that is logged when more than 15 consecutive 0s or fewer 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”.
Explicit Congestion Management: The method used in frame relay to notify the terminal equipment that the network is overly busy. The use of FECN and BECN is called explicit congestion management. Some
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