Page 262 - Electrical Engineering Dictionary

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nal (ENI ) or the inverting input terminal The recording process uses e.g., the “laser
−
(ENI ) and represents the total noise con- power modulation” or the “magnetic field
tributed by the op amp if either input terminal modulation” technique.
is open circuited.
erasable programmable read-only mem-
equivalent noise temperature an alter- ory (EPROM) a nonvolatile chip mem-
native way of describing the noise properties ory, itisusedintheplaceofPROM.EPROMs
of two port networks. presents a glass on the case that allows one
to see the chip. They can be erased by ex-
equivalent noise voltage (ENV) a noise posing the chip at the ultraviolet light for
voltage source that is effectively in series typically 20 minutes. Once erased they can
with either the inverting or noninverting in- be reprogrammed. The programming has
put terminal of the op amp and represents the to be performed by using a special algo-
total noise contributed by the op amp if the rithm and a supplementary V pp . Also called
inputs were shorted. UVPROM. See also electronically erasable
programmable read-only memory.
equivalent reactance the reactance of the
windings of an electromagnetic machine re- erasure in a forward error control sys-
flected to one side (component) of the ma- tem, a position in the demodulated sequence
chine. See also equivalent impedance. where the symbol value is unknown. De-
pending on the quality of the received signal
equivalentresistance theresistanceofthe when no decision is made on a particular bit,
windings of an electromagnetic machine re- the demodulator inserts an erasure in the de-
flected to one side (component) of the ma- modulated data. Using the redundancy in the
chine. See also equivalent impedance. transmitted data, the decoder attempts to fill
in the positions where erasures occurred. See
equivalent source fictitious source used binary erase channel.
in the equivalence theorem.
erbium doped fiber amplifier (EDFA)
equivalentsphereillumination(ESI) the an optical amplifier based on the rare-earth
level of sphere illumination that would pro- erbium that can amplify optical signals in
duce task visibility equivalent to that pro- the 1550 nm telecommunications window.
duced by a specific lighting environment. The useful gain region extends from approx-
imately 1530 nm to 1565 nm.
equivalentsystemdynamics adynamical
system model resulting from substituting the EREW See exclusive reads and exclusive
equivalent control into the plant’s modeling writes.
equation. The equivalent system’s trajectory
is confined to a surface that is parallel to the ergodic process a process that has all pos-
sliding surface if the system’s initial condi- sible ergodic properties.
tion is off the sliding surface. If the initial For process X(t) when the time average
condition is on the sliding surface, then the
Z T/2
equivalent system’s trajectory will stay on the
lim (1/T ) X(t)dt
sliding surface. T →∞ −T/2
erasable optical disk a magneto-optical exists and equals the corresponding expected
disk that can be both read/written and value E [X(t)], it is said that X(t) is ergodic
erased. A thermo-magneto process is used in the mean. There are ergodic properties as-
for recording and erasure of information. sociated with the mean, autocorrelation, and

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