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Technology Glossary


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Select a letter above to access the technology glossary in alphabetical order.
Select + for miscellaneous.

E.164 - A public network addressing standard utilizing up to a maximum of 15 digits. ATM uses E.164 addressing for public network addressing.

E1 - Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 2.048 Mbps. E1 lines can be leased for private use from common carriers.

E3 - Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 34.368 Mbps. E3 lines can be leased for private use from common carriers.

Earthquake Protection Bracing - The additional bracing required in seismic areas where quakes or tremors are possible.

Edge Device - A physical device which is capable of forwarding packets between legacy interworking interfaces (e.g., Ethernet, Token Ring, etc.) and ATM interfaces based on data-link and network layer information but which does not participate in the running of any network layer routing protocol. An Edge Device obtains forwarding descriptions using the route distribution protocol.

EDI (Electronic Data Interchange) - A series of standards which provides computer to computer data exchange over phone lines between differing computer types.

Editor - A software program used to modify programs or files while they are being prepared or after they are complete.

EEPROM (Electrically Erasable Programmable Read Only Memory)- an EPROM that can be cleared with electrical signals rather than the traditional ultraviolet light.

EFCI (Explicit Forward Congestion Indication) - The second bit of the payload type field in the header of an ATM cell, the EFCI bit indicates network congestion to receiving hosts. On a congested switch, the EFCI bit is set to "1" by the transmitting network module when a certain number of cells have accumulated in the network module's shared memory buffer. When a cell is received that has its EFCI bit set to "1," the receiving host notifies the sending host, which should then reduce its transmission rate.

Efficiency - The ratio of output energy to input energy, expressed in percent.

Efficiency (for power supplied) - The total output power (usually in watts) divided by the input power with a given load. In equation form, percent efficiency at a specified load is: % Efficiency = (output / input) 100 or 1 -(losses / input) 100 where losses, output and input are expressed in watts.

EGP (Exterior Gateway Protocol) - Used by gateways in an internet, connecting autonomous networks.

Egress - One of two distinctly different roles of the MPC (Multi Protocol Client). As an Egress MPC the client sinks or receives data frames from an Ingress MPC (Multi Protocol Client).

egress - When referring to a switch, fabric or port, egress typically refers to the output, transmit or downstream side.

EIA (Electronics Industries Association) - a USA trade organization that issues its own standards and contributes to ANSI; developed RS-232. Membership includes USA manufacturers.

EISA (Extended Industry Standard Architecture) - a bus architecture for desktop computers that provides a 32-bit data passage while maintaining compatibility with the ISA or AT architecture.

ELAN (Emulated Local Area Network) - A logical network initiated by using the mechanisms defined by LAN Emulation. This could include ATM and legacy attached end stations.

elarp - A Marconi program that shows and manipulates MAC and ATM address mappings for LAN Emulation Clients (LECs).

Elastic - Applications adjust their demands in real time based on feedback about available network bandwidth, they run "Closed Loop". Best-Effort data applications are usually elastic (i.e. TCP, NFS, ABR). They use as much bandwidth as they can if it is available, but less when it is unavailable.

elconfig - A Marconi program that shows and modifies LEC configuration. Allows the user to set the NSAP address of the LAN Emulation Configuration Server (LECS), display the list of Emulated LANs (ELANs) configured in the LECS for this host, display the list of ELANs locally configured along with the membership state of each, and locally administer ELAN membership.

Electrolyte - Non-metallic conductor of electricity in which current is carried by the physical movement of ions.

Electromotive Force - Force that produces or tries to produce a movement of electric charges; and electric current.

Electronic Central Office - Modern telephone central office using solid state devices (not electromechanical switches). Typically digital.

Electronic Voice Mail - A system which stores messages spoken by a user, usually over a telephone, which can be retrieved by the intended recipient when that person next calls into the system. Also called Voice Mail, it operates just like a touch-tone controlled answering machine.

Electrostatic - Pertaining to electric charges at rest, with no electric current flowing.

Electrostatic Field - Region in which there is electric stress resulting from electrostatically charged bodies.

EM - the CellPath 300 extension module; paired with the system controller and supporting an optional PCMCIA card.

Embedded SNMP Agent - An SNMP agent can come in two forms: embedded or proxy. An embedded SNMP agent is integrated into the physical hardware and software of the unit. The CellPath 300 has an internal, integrated SNMP agent.

EMI (Electromagnetic Interference) - signals generated and radiated by an electronic device that cause interference with radio communications, among other effects.

End Cells - Extra storage cells in a battery string which are switched into service to aid the usual 23 cells if the rectifier fails temporarily, in order to maintain the required voltage on the switching equipment (intended to extend reserve time of batteries).

End System - A system where an ATM connection is terminated or initiated. An originating end system initiates the ATM connection, and a terminating end system terminates the ATM connection.

End-to-End Connection - When used in reference to an ATM network, a connection that travels through an ATM network, passing through various ATM devices and with endpoints at the termination of the ATM network.

End-User - The premises occupant who uses and pays the monthly charges for the services received, and does not resell it to others.

Energized - The activated state of a relay or circuit.

Engine Alternator - Generates standby AC power to sustain the essential load during commercial power failure. The alternator may be powered by a gas turbine, diesel, or gasoline engine.

Engine/Alternator Alarms - (1) A group of discrete alarms or status indicators emanating from the standby power system. Outputs can be normally picked up at the engine alarm cabinet (SD81223 01). Other connection points could be the transfer breaker and/or engine control cabinet. (2) Major and minor visual and audible grouping is taken from the engine alarm cabinet for automatic systems.

Enterprise - Terminology generally referring to customers with multiple, non-contiguous geographic locations.

Entry Border Node - The node which receives a call over an outside link. This is the first node within a peer group to see this call.

EPD(Early Packet discard)- A mechanism used by some ATM switches to avoid unwanted congestion in packet traffic. If the amount of the buffer space consumed at an outgoing port exceeds a threshold, EPD discards new packets while packets already partially transmitted remain unaffected.

EPROM (Erasable Programmable Read Only Memory) - A PROM which may be erased and rewritten to perform new or different functions (normally done with a PROM burner).

Equivalent Capacity - The unit of measure for resource consumption on a link, expressed in cells per second.

EQL (Equalization) - The process of compensating for line distortions.

Equalizing Center - Main discharge leads from a power plant BCB connected together on a cable rack in the main aisle of the equipment room to a main aisle feeder. The feeder is then tapped with leads going to a protection device to supply DC power equipment in a line-up.

Equalizing Charge - A routine charge applied to storage cells in an effort to equalize the voltage across them to the same value.

Equipment Cabinet - The cabinet or box which houses relays, circuit boards or other apparatus. Usually also contains the power supply to convert the 120 volt AC current into the low voltage direct current necessary to run the system.

Equipment Failure - When a hardware fault stops the successful completion of a task.

ER (Explicit Rate) - The Explicit Rate is an RM-cell field used to limit the source ACR to a specific value. It is initially set by the source to a requested rate (such as PCR). It may be subsequently reduced by any network element in the path to a value that the element can sustain. ER is formatted as a rate.

ES (End System) - A system in which an ATM connection is terminated or initiated. An originating end system initiates the ATM connection, and a terminating end system terminates the ATM connection. OAM cells may be generated and received.

ES (Errored Second) - A second during which at least one code violation occurred.

ESF (Extended Super Frame) - A T1 framing format that utilizes the 193rd bit as a framing bit, but whose Superframe is made up of 24 frames instead of 12 as in D4 format. ESF also provides CRC error detection and maintenance data link functions.

ESI (End System Identifier) - This identifier distinguishes multiple nodes at the same level in case the lower level peer group is partitioned.

ESN (Electronic Serial Number) - Each cellular phone is assigned an ESN which is automatically transmitted to the base station every time a cellular call is placed. The Mobile Telephone Switching Office checks the ESN to make sure it is valid, that the phone has not been reported stolen, that the user’s monthly bill has been paid, etc., before permitting the call to go through.

ESS (Electronic Switching System) - A designation for the switching equipment in Bell System central offices. In the independent telephone company industry, the abbreviation is EAX.

Essential AC Load - A load that must operate during prolonged loss of commercial power. It must be connected to the standby power source and be able to tolerate an interruption of ten seconds or more.

ETACS (Extended TACS) - The conventional cellular technology used in the United Kingdom and other countries. It is developed from the U.S. AMPS technology.

Ethernet - A 10-Mbps, coaxial standard for LANs in which all nodes connect to the cable where they contend for access.

Exception - A connectivity advertisement in a PNNI complex node representation that represents something other than the default node representation.

Excessive Zeroes (EXZ) Error Event - An Excessive Zeroes error event for an AMI-coded signal is the occurrence of more than fifteen contiguous zeroes. For a B8ZS coded signal, the defect occurs when more than seven contiguous zeroes are detected.

Exchange - (1) A room or building equipped so that telephone lines terminating there may be interconnected as required; and (2) switching exchange: an aggregate of traffic-carrying devices, switching stages, controlling and signaling means at a network node that enables subscriber lines and/or other telecommunication circuits to be interconnected as required by individual callers.

Exterior - Denotes that an item (e.g., link, node, or reachable address) is outside of a PNNI routing domain.

Exterior Link - A link that crosses the boundary of the PNNI routing domain. The PNNI protocol does not run over an exterior link.

Exterior Reachable Address - An address that can be reached through a PNNI routing domain, but which is not located in that PNNI routing domain.

Exterior Route - A route that traverses an exterior link.

External Alarms - General description given to alarms which are then transferred from central office to a remote surveillance center.