18WuD2x

266 error correction • ET
especially in magnetic data storage media, such as
tapes and disks. 2. In digital communications, any
scheme in which the receiver (destination) automatically
eliminates (to the greatest possible extent)
errors in data from a transmitter (source). For
example, the destination can instruct the source
to repeat questionable characters or words.
error-correction routine In computer operations,
a series of programmed instructions to detect and
correct errors in files. A common example is a
spell-checking program for word-processed document
files.
error current An error signal that is a feedback
current for automatically correcting a system.
error curve A bell-shaped curve that describes the
distribution of errors in measurement around a
true value.
error-detecting code In computer operations, a
character-coding system that ensures that an impossible
combination (forbidden characters) will
be generated by an error (for error detection).
error-detecting routine A computer program that
detects errors by checking the validity of data.
error detection and feedback In computer operations,
a system in which an error (sensed by an
error-detecting code) automatically generates a
request to repeat the suspect signal.
error detector A sensor that responds to an error
signal by delivering a signal proportional to the
error.
error diagnostics As performed by a compiler, detecting
and indicating the presence of errors in
source language statements.
error interrupt A computer program halt caused
by a software or hardware error and accompanied
by a display of what has happened.
error list As produced by a compiler, a list of
source language statement faults.
error message During a computer program run, a
statement (displayed on a peripheral) of what is
in error.
error of measurement The positive or negative difference
between the value of an actual measurement
and the true (or most probable) value.
error range For a data item, the range of values
over which it will cause an error.
error rate In data transmission, the ratio of errors
transmitted to the data transmitted.
error-rate damping Damping that involves adding
to an error signal another signal that is proportional
in rate of change.
error ratio 1. In a received message, the number of
incorrect characters divided by the total number
of characters. Can be represented as a fraction
between 0 and 1 or as a percentage by multiplying
the fraction by 100. 2. A measure of distortion
for digital signal communications. The number of
inaccurately received bits divided by the total
number of received bits.
error routine A computer program segment that is
input when an error is detected so that an
appropriate action is taken (correct the error, repeat
the process, etc.).
error-sensing circuit A circuit that samples the
output current or voltage of a power supply, amplifier,
or control system, compares this output
with a standard value, and delivers a feedback
(correction) signal whose amplitude is proportional
to the difference (error).
error signal In a servo system, an output signal
whose value is proportional to the difference between
the actual operating quantity of the system
and a standard reference quantity. The signal is
fed back to the input of the system for automatic
correction.
error tape In data processing, a record tape designed
and used for storing errors for subsequent
study.
error voltage An error signal that is a feedback
voltage for automatically correcting a system.
Es Symbol for EINSTEINIUM.
Esaki diode See TUNNEL DIODE.
E scope See E DISPLAY.
escape character In computer operations, a character
indicating that the next character belongs
in a new group.
escapement A (usually oscillating) mechanical or
electromechanical device that stores energy (often
in a spiral spring) on one swing, and returns that
energy on the next swing. Such a mechanism advances
a shaft progressively in a clock or watch,
and in some control equipment.
escape velocity 1. The minimum velocity (about
25,000 miles per hour or seven miles per second)
required for a space vehicle to completely escape
the gravitational field of the earth. 2. The minimum
velocity required for a space vehicle to completely
escape the gravitational field of a planet or
star. 3. The minimum velocity required for an
electron to escape the electrical influence of an
atomic nucleus.
escutcheon A usually decorative plate that
frames an opening or covers a panel in a piece of
equipment (e.g., the escutcheon of a radio tuning
dial).
ESD Abbreviation of ENERGY-STORAGE DEVICE.
ESG Abbreviation of electronic sweep generator.
Esnault-Pelterie formula A formula for approximately
calculating the inductance of a singlelayer
solenoidal coil:
L = 0.1008(a 2 n 2 )/(s + 0.92a)
where L is the coil inductance in microhenrys, a
is the radius of the coil in inches, s is the length
of the coil in inches, and n is the number of turns
in the winding. The formula is accurate to 0.1
percent for all values of 2a/s between 0.2 and
1.5.
ESS Abbreviation of electronic switching system.
EST Abbreviation of EASTERN STANDARD TIME.
esu Abbreviation of ELECTROSTATIC UNIT(S).
ET Abbreviation of EPHEMERIS TIME.