Located within the connector, the ferrule securely holds the aluminum sheath of the cable and makes a good ground. As the nut is tightened to the entry barrel, the inclines on the ferrule and entry barrel mate, closing onto the sheath. [Arr11]
The field-effect transistor (FET) is a transistor that relies on an electric field to control the shape of the nonconductive depletion layer within a semiconductor material, thus controlling the conductivity of a "channel" in that material. FETs, like all transistors, can be thought of as voltage-controlled resistors. Most FETs are made using conventional bulk semiconductor processing techniques, using the single-crystal semiconductor wafer as the active region, or channel. The channel region of TFTs (thin-film transistors), on the other hand, is a thin film that is deposited onto a substrate (often glass, since the primary application of TFTs is in liquid crystal displays. For more on TFTs, see thin-film transistor; the remainder of this article deals with the transistors most commonly used in integrated circuits. In biology, voltage-gated ion channels work in a similar way. The terminals in FET are called gate, drain and source. (Compare these to the terminology used for bipolar junction transistors (BJTs): base, collector and emitter.) The voltage applied between the gate and source terminals opens and closes the conductive channel, modulating the resistance between source and drain. The FET is simpler in concept than the bipolar transistor and can be constructed from a wide range of materials. The different types of field-effect transistors can be distinguished by the type of insulation between channel and gate:
The MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) utilizes an insulator (typically SiO2).
Power MOSFETs become less conductive with increasing temperature and can therefore be thought of as n-channel devices by default. Silicon devices that use electrons, rather than holes, as the majority carriers are slightly faster and can carry more current than their P-type counterparts. The same is true in GaAs devices.
Power MOSFETs are typically Vertical-FETs, where the active device is built along the rims of hexagonal pits in the semiconductor surface, and the Drain current flows vertically down the surface of the pits.
The JFET (Junction Field-Effect Transistor) uses a p-n junction to produce the depletion layer.
Substituting the p-n-junction with a Schottky barrier gives a MESFET (Metal-Semiconductor Field-Effect Transistor), used for GaAs and other III-V semiconductor materials.
Using bandgap engineering in a ternary semiconductor like AlGaAs gives a HEMT (High Electron Mobility Transistor), also named an HFET (heterostructure FET). The fully depleted wide-band-gap material forms the isolation.
The distinguishing feature of the TFT (thin-film transistor) is the use of amorphous silicon or polycrystalline silicon as the channel. [Wor11]
Frequency-Hopping Spread Spectrum; a spread-spectrum method of transmitting signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. A spread-spectrum transmission offers three main advantages over a fixed-frequency transmission:
Spread-spectrum signals are highly resistant to noise and interference. The process of re-collecting a spread signal spreads out noise and interference, causing them to recede into the background.
Spread-spectrum signals are difficult to intercept. A Frequency-Hop spread-spectrum signal sounds like a momentary noise burst or simply an increase in the background noise for short Frequency-Hop codes on any narrowband receiver except a Frequency-Hop spread-spectrum receiver using the exact same channel sequence as was used by the transmitter.
Spread-spectrum transmissions can share a frequency band with many types of conventional transmissions with minimal interference. The spread-spectrum signals add minimal noise to the narrow-frequency communications, and vice versa. As a result, bandwidth can be utilized more efficiently. [Wor11]
A material and element that may be used to protect an optical fiber waveguide from physical damage, providing mechanical isolation and/or protection. [Arr11]
There are numerous types of plugs and sockets to connect optical fibers, using threaded, bayonet, push-pull and snap-lock connections. The first fiber-optic connector to be standardized was SMA, which was followed by the SC, ST and FC types. Since most optical transmissions require two cables (one to transmit and the other to receive), smaller form factors such as the snap-lock Fiber Jack were developed to make installations as simple as plugging in a telephone. Attaching a connector to an optical fiber takes more work than copper wire connectors. The ends of the fiber usually have to be carefully cemented and then polished in order to let the maximum light pass through. Most class time on the subject is "hands on." See mechanical splice and fusion splice. [PCM01]
Fiber Distributed Data Interface (FDDI)
A network based on the use of optical fiber to transmit data at a rate of 100Mbps. Or a fiber-based LAN standard.
A point of interface between a fiber trunk and the coaxial distribution.
(1) Very thin and pliable tubes of glass or plastic used to carry wide bands of frequencies. (2) Transmission medium that uses glass or plastic fibers vs. other, copper-based wires to transmit data or voice signals. Fiber-optic cable offers much greater capacity and transmission speeds than traditional mediums. Also, the branch of optical technology concerned with the transmission of radiant power through fibers made of transparent materials such as glass, fused silica or plastic. [Pho11]
Any optical transmission channel designed to connect two end terminals or to be connected in series with other channels. [Arr11]
One half of a complete picture (or frame) interval, containing all of the odd or even scanning lines of the picture.
The rate at which a complete field is scanned, nominally 60 times a second.
Field Strength Meter (FSM)
See Signal level meter.
Figure 8 Cable
Coaxial cable manufactured with an integrated messenger cable. [Arr11]
File & Print Sharing
A network component which allows a user to share files or printers on their computer with others on the network.
File Transfer Protocol (FTP)
A method used to exchange files between computers on a network or the Internet using the TCP/IP protocol. It can also be the verb used to describe that transfer (“I need to FTP a file to them”).
A circuit that selects the frequency of desired channels. Used in trunk and feeder lines for special cable services such a two-way operation.
Federal Information Processing Standard
Foreign Intelligence Surveillance Act
The Failures In Time (FIT) rate of a device is the number of failures that can be expected in one billion (109) device-hours of operation. (e.g. 1000 devices for 1 million hours or 1 million devices for 1000 hours each, or some other combination.) This term is used particularly by the semiconductor industry. Read more: http://www.answers.com/topic/failure-rate#ixzz1H3U5xUYj [Ans11]
Fiber In The Loop; a PSTN architecture consisting of a fiber optic access network.
Fixed Mobile Convergence (FMC)
Both FMC and Femtocell technologies are primarily focused on providing adequate mobile phone service in environmental circumstances that are less than optimal for the existing cellular infrastructure. FMC is basically a dual-mode phone that uses Wi-Fi based networks for interior phone connectivity as well as the normal cellular technology to provide ubiquitous connectivity regardless of the physical location. Femtocell technology offers the same results, but does not require a phone with two different wireless technologies. Femtocell technology uses cellular (3G) base stations which are connected to the Internet located at building interior locations that are associated with poor cellular reception. The 3G phone then transitions between Femtocells and the telco’s cellular infrastructure depending on which one provides more optimal RF signal conditions. [Tec112]
IP Multimedia Subsystem (IMS) Infrastructure for FMC, courtesy of Azimuth Systems, http://www.azimuthsystems.com/