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fax machine or fax terminal

Facsimile transfer machines for sending and receiving images and written material over a telephone line. Almost all fax machines today use the CCITT Group 3 protocol. A higher performance protocol, CCITT Group 4, is available for ISDN. See also G3FE, Group 3 fax.

fax license unit

In NaturalFax, fax license units are used to measure and control the number of active fax sessions in a system. If an application does not explicitly allocate fax license units, NaturalFax functions automatically allocate fax license units as required.

fax session

According to the ITU T.30 specification, and as used in NaturalFax, the portion of a fax transfer operation which begins with the called fax terminal sending its capabilities (Phase B) to the calling application or fax terminal and ends with the calling fax terminal commanding a disconnect (Phase E). See also Group 3 fax, Phase B, Phase E, T.30.

FCC

Federal Communications Commission; the US government agency that regulates and monitors interstate communications, and the use of the electromagnetic spectrum.

FIFO

First In, First Out; refers to a queue where entries are processed in the order in which they were received.

fill

Data which may be added to the image data without appearing in or affecting the image. This added data will delay the appearance of the image at the destination side in order to match encountered network delays.

flash hook

A brief signaling state change which goes from off-hook to on-hook, and back to off-hook. See also off-hook, on-hook.

flat file

A file that contains only data (no header or control information).

FMIC

A Flexible MVIP Interface Circuit; a circuit which provides a digital timeslot switch and an MVIP bus interface.

formant synthesizer

A DSP software module that receives digital sound data and produces sound output (in the case of NaturalText, the sound of a human voice).

forward connection

A type of full-duplex switch connection. In MVIP-90, this describes the mapping of full-duplex connections so that the lower 8 output streams tie to input of the switch block and the output of the switch block is tied to the lower 8 input streams. See also full-duplex, reverse connection.

four-wire

In analog telephony, a transmission path that requires four physical conductors for the voice path, one pair for each direction (any additional wires required for signaling are not counted). In digital telephony, a transmission path that physically separates transmit and receive channels or timeslots. See also two-wire.

FPGA

Field Programmable Gate Array; for QX 2000 boards, a circuit which provides internal glue logic.

frame (data)

The basic data transmission unit used in bit-oriented protocols. A flag bit (also called a framing bit) at either end of the frame marks the beginning and end of an individual frame. Because a frame format is clearly defined, and conforms to a specific structure, network equipment can recognize the meaning and purpose of specific bits of data.

frame (Diva)

In the Diva SDK, a structure which contains PCM data that has been packaged in 80 byte buffers.

frame (speech)

The smallest set of samples (sometimes including optional headers or trailers) that a speech compression algorithm requires. Typically, a speech buffer contains multiple frames.

frame (T1/E1)

A portion of a PCM data stream that contains one binary data word, typically 8 bits, for each unidirectional channel. A frame usually will also contain control and synchronization bits. Each frame is 125 microseconds long.

FSK

Frequency Shift Keying; a type of analog modem signal that uses two frequencies to send ones and zeroes.

FTP

File Transfer Protocol; a standard TCP/IP utility for transferring files between hosts over a packet-switched network.

full crosspoint switch

A switch in which any element can be connected to any other element.

full-duplex

Simultaneous two-way voice or two-way signal data transmission. See also half-duplex, simplex.

Full Hot Swap

A system model requiring Full Hot Swap boards on a CompactPCI platform. Full Hot Swap boards include a blue LED for Hot Swap signaling and switches in the ejector handles to control the hardware state of the board. See also hot swap.