Multi-Tech Systems MT4X56USB - Manual (Page 84)

MultiModemUSB User Guide
MT4X56USB 84
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. Both ESF and B8ZS are typically 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.
Foreign Exchange Office (FXO): Provides local telephone service from a CO outside of (“foreign” to) the subscriber’s
exchange area. In simple form, a user can pick up the phone in one city and receive a tone in the foreign city. Connecting a
POTS telephone to a computer telephony system via a T1 link requires a channel bank configured for the FX connection. To
generate a call from the POTS set to the computer telephony system, a FXO connection must be configured.
Foreign Exchange Station (FXS): See FX, FXO. To generate a call from the computer telephony system to the POTS set,
an FXS connection must be configured.
Forward Explicit Congestion Notification (FECN): A bit that tells you that a certain frame on a particular logical
connection has encountered heavy traffic. The bit provides notification that congestion-avoidance procedures should be
initiatedin the same direction of the received frame. See also BECN (Backward Explicit Congestion Notification).
Function: A Universal Serial Bus device that provides a capability to the host. For example, an ISDN connection, a digital
microphone, or speakers.
G
Gateway: 1. A functional unit that interconnects two computer networks with different network architectures. A gateway
connects networks or systems of different architectures. A bridge interconnects networks or systems with the same or
similar architectures. 2. A network that connects hosts.
Graphical User Interface (GUI): A type of computer interface consisting of a visual metaphor of a real-world scene, often
of a desktop. Within that scene are icons, representing actual objects, that the user can access and manipulate with a
pointing device.
H
Handshaking: A process that two modems go through at the time of call setup to establish synchronization over the data
communications link. It is a synchronization and negotiation process accomplished by the exchange of predefined, mutually
recognized control codes.
Hexadecimal: A base 16 numbering system used to represent binary values. Hex uses the numbers 0-9 and the letters A-F:
usually notated by an “h” (e.g., “4CF h”, read “four charley fox, hex”). The result is that one hex digit represents a 4-bit
value.
High-level Data Link Control (HDLC): An ISO standard, bit-oriented data communications protocol that provides nearly
error-free data transfers.
Host: The host computer system where the Universal Serial Bus host controller is installed. This includes the host hardware
platform (CPU, bus, etc.) and the operating system in use.