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Echo cancellation - A DSP technique that filters unwanted signals caused by echoes from the main audio source.
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Echo suppression - Used in telephone networks to reduce the impact of echo and thereby improve voice quality. The impact of echo suppression is usually to limit data transmission to one direction at a time. In order to provide for duplex operation, modems request telephone systems to turn off echo suppression.
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ECL - Emitter Coupled Logic. A family of high speed, low power IC logic devices. Also called “current mode logic.”
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Edge-to-edge - Describes common density factors in loudspeaker layout designs. Edge-to-edge density places the speakers such that the outside edges of their sound cones just touch one another.
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EDID - Extended Display Identification Data - EDID is a data structure used to communicate video display information, including native resolution and vertical interval refresh rate requirements, to a source device. The source device will then output the optimal video format for the display based on the provided EDID data, ensuring proper video image quality. This communication takes place over the DDC – Display Data Channel.
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EDID Minder® - A proprietary EDID management process from Extron. EDID Minder® automatically manages the EDID information between a digital display device and one or more input sources. By maintaining continuous EDID communication with all sources, EDID Minder® ensures that digital sources power up properly and maintain their video output, whether or not they are actively connected to the digital display device.
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EDTV - Enhanced Definition Television. A new digital TV product category added between High Definition TV (HDTV) and Standard Definition TV (SDTV), with the following attributes: a receiver that accepts ATSC terrestrial digital transmissions and decodes all ATSC Table 3 video formats; a display scanning format with active vertical scanning lines of 480 progressive (480p) or higher; no aspect ratio specified; and receives and reproduces, and/or outputs Dolby Digital audio.
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EEPROM - Electrically Erasable Programmable Read-Only Memory. The information in an EEPROM is erased by exposing it to an electrical charge. Similar to EPROM except in the way in which information is erased.
Also see "Flash memory."
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Effective modal bandwidth – EMB - In fiber optics, the modal bandwidth of a multimode fiber when using a laser as a light source. EMB is sometimes referred to as laser launch bandwidth.
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EGA - Enhanced Graphics Adapter. Introduced by IBM in 1984, this replaced CGA (Color Graphics Adapter).
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EIA - Electronics Industries Association. The association that determines recommended audio and video standards in the US.
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EIA sync - The standard broadcast sync, also called EIA-RS-170.
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EIA-RS-170 - The standard broadcast sync as determined by the Electronics Industries Association. Commonly called EIA sync.
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Electrode - In a fusion splicer, the component which discharges electricity to enable two optical fibers to be fused or welded together.
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Electron gun - The part in the CRT that produces the electron beam attracted to the phosphor-coated back surface of the screen. The beam strikes the phosphors, causing them to emit red, green, or blue light, creating images on the screen.
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Electrostatic focus - Also referred to as electrostatic deflection. A CRT tube focusing method that uses electrically charged plates instead of deflection coils to focus the electron beam. This method was used only on small CRTs because the larger the CRT, the higher the voltage required, which can cause harmful x-rays to be emitted.
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ELFEXT - Equal Level Far End Crosstalk. The amount of crosstalk at the far end after compensation for attenuation over a run.
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Embedded data - Digital technologies such as SDI, HD-SDI, and HDMI, can carry variety of other data along with the primary video data, including audio, control, metadata such as content title or other identifying information, or other ancillary information. These data are said to be embedded, as they travel with the primary signal from the source device to the destination.
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EMI - Electromagnetic Interference. Any electromagnetic disturbance that interrupts, obstructs, or otherwise degrades or limits the effective performance of electronics/electrical equipment.
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Encoder - A device, often built into video cameras, that changes individual component signals into composite signals. For example, an encoder combines Y (luma) and C (chroma) signals to produce a video image.
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Encoding - In video, the combination of electronic elements into one signal; for example, S-video is encoded (combined) to create a composite video signal.
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Encryption - To manipulate information into a coded form that cannot be read without a device that will unscramble the code. Video signals are also scrambled in cable and pay-TV systems so that the viewer must pay to receive the program after it has been electronically deciphered.
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End Finish - The endface of an optical fiber at the ferrule, finished or polished to be smooth in order to minimize signal loss or backreflection. PC, SPC, UPC, and APC polishing finishes are available for singlemode connectors.
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Entrance Facility - In fiber optic applications, the entrance to a building for fiber optic cables.
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Epoxy - An adhesive that bonds between surfaces by means of a chemical reaction in which the adhesive cures as it dries. Epoxy is used in fiber optic applications to adhere a connector ferrule to the fiber.
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EPROM - Erasable Programmable Read Only Memory. A device that can store information (instructions or data) and retain it when power is removed. An EPROM is erased by exposing it to ultraviolet light. New information is loaded into the EPROM using a PROM programmer or “burner.”
Also see "Flash memory."
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EQ (Audio) - Equalizer. An audio signal processor used to add or attenuate frequencies in order to change the character of the resulting sound. EQ’s are properly used with a reference signal (see pink noise) and a real- time analyzer to ensure that the sound from the speakers closely matches the original sound.
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EQ (Video) - Equalization. Selective amplification (signal restoration) applied to a signal to compensate for high frequency attenuation and other distortions encountered in long lengths of cable.
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Equalizing pulses - These pulses cause the vertical deflection to start at the same time in each interval. They also keep the horizontal sweep circuits in step during the portions of the vertical blanking interval immediately preceding and following the vertical sync pulse.
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Error detection and correction - The ability to detect errors caused by interference or other factors during the transmission of a signal, and then reconstruct the received signal so that it is a faithful reproduction of the original signal, without errors. A process known as Forward Error Correction is often used to allow the receiver to detect and correct some errors without having to “ask” the transmitter to send additional data.
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Ethernet - A network protocol that uses MAC addresses to exchange data between computers. Using ARP, with TCP/IP support, Ethernet devices can be connected to the Internet. An Ethernet LAN typically uses unshielded twisted pair (UTP) wires. Today’s Ethernet systems provide transmission speeds of 10 Mbps or 100 Mbps. Ethernet is mostly based on the IEEE 802.3 standard.
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Expansion slots - Slots inside a cabinet that are used to connect additional circuit modules (cards).
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Extrinsic Joint Loss - The portion of optical signal loss at a joint that is not intrinsic to the optical fibers, usually caused by misalignment between the fibers, end separation, and imperfections in the end finish of either fiber.
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Eye Pattern - The representation of a digital signal on an oscilloscope in which a digital data signal is repetitively sampled. Distortion in the signal waveform due to interference and noise appears as closure of the eye pattern. Signals that are poorly synchronized with the system clock (also known as jitter), too high, too low, too noisy, too slow to change, or which have too much undershoot or overshoot, can be observed from the eye pattern. Eye patterns are used to evaluate the quality of digital signals when passed through cables or signal extension devices, switchers, signal processors, and other electronics.
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