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ProxyServer User Guide
E
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.
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.
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 end-to-end protocols use FECN
or BECN, but usually not both options together. With this method, a congestion condition is identified and fixed before it
becomes critical. Contrast with "implicit congestion".
Extended Super Frame (ESF): One of two popular formats for framing bits on a T1 line. ESF framing has a 24-frame
super-frame, where robbed bit signaling is inserted in the LSB (bit 8 of the DS-0 byte) of frames 6, 12, 18 and 24. ESF has
more T1 error measurement capabilities than D4 framing. ESF and B8ZS are typically both offered to provide clear channel
service.
F
Failed Seconds: A test parameter where the circuit is unavailable for one full second.
Failed Signal: A T1 test parameter logged when there are more than 9 SES (Severely Errored Seconds).
Fax (facsimile): Refers to the bit-mapped rendition of a graphics-oriented document (fax) or to the electronic transmission
of the image over telephone lines (faxing). Fax transmission differs from data transmission in that the former is a bit-
mapped approximation of a graphical document and, therefore, cannot be accurately interpreted according to any character
code.
Firmware: A category of memory chips that hold their content without electrical power, they include ROM, PROM, EPROM
and EEPROM technologies. Firmware becomes "hard software" when holding program code.
Foreground: The application program currently running on and in control of the PC screen and keyboard. The area of the
screen that occupies the active window. Compare with "background".
Fractional T1 (FT1): A digital data transmission rate between 56 Kbps (DS0 rate) and 1.544M bps (the full T1 rate - in
North America). FT1 is typically provided on 4-wire (two copper pairs) UTP. Often used for video conferencing, imaging and
LAN interconnection due to its low cost and relatively high speed. FT1 rates are offered in 64 Kbps multiples, usually up to
768 Kbps.
Frequency: A characteristic of an electrical or electronic signal which describes the periodic recurrence of cycles.
Frequency is inversely proportional to the wavelength or pulse width of the signal (i.e., long wavelength signals have low
frequencies and short wavelength signals yield high frequencies).
Foreign Exchange (FX): A CO trunk with access to a distant CO, allowing ease of access and flat-rate calls anywhere in
the foreign exchange area.
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MTPSR1-202ST
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