18WuD2x

E avg • echo 225
Symbol for AVERAGE VOLTAGE.
Symbol for BATTERY VOLTAGE.
E bend In a waveguide, a smooth change in the direction
of the axis, which remains parallel to the
direction of polarization.
EBI Abbreviation of EQUIVALENT BACKGROUND
INPUT.
ebiconductivity Conductivity resulting from electron
bombardment.
ebonite Hard rubber used as an insulant. Dielectric
constant: 2.8. Dielectric strength: 30 to 110
kV/mm.
EBR Abbreviation of ELECTRON-BEAM RECORD-
ING.
EBS Abbreviation of ELECTRON-BOMBARDED
SEMICONDUCTOR.
E avg
E b
Magnetic pole
Earth
Magnetic pole
earth’s magnetic field
Flux lines
EBS amplifier An amplifying device using an electron-bombarded
semiconductor. The electron
beam is modulated by the input signal, and the
modulated resistance of the semiconductor target
modulates a relatively heavy current to provide
an amplified output. Current gains on the order
of 2000 are possible.
ec Abbreviation of ENAMEL-COVERED (in reference
to wire).
eccentric circle See ECCENTRIC GROOVE.
eccentric groove On a phonograph record, an offcenter
groove in which the stylus rides at the end
of the recording, where it causes the tone arm to
trip the record-changing mechanism.
eccentricity 1. The condition of being off center,
intentionally or not. It is often a consideration in
the behavior of dials, potentiometers, and servomechanisms.
2. On a phonograph record, the
condition in which the spiral recording groove
and the center hole of the disk are not concentric.
3. A quantitative expression for the extent to
which an ellipse is elongated.
eccentricity of orbit The extent to which the orbit
or path of a satellite differs from a circle. A
circular orbit has eccentricity zero. As the orbit
becomes elliptical and deviates more and more
from a perfect circle, the eccentricity increases.
When the eccentricity reaches 1, the object takes
a parabolic path through space. If the eccentricity
exceeds 1, the path is a hyperbola.
ECCM Abbreviation of ELECTRONIC COUNTER-
COUNTERMEASURES.
ECDC Abbreviation of electrochemical diffused collector.
ECG Abbreviation of electrocardiogram. (Also,
EKG.)
ECG telemetry Use of a radio telemetering system
to monitor the heart function of a person from a
distance.
echelon 1. A level of calibration accuracy, the
highest echelon being the national standard for
the particular measurement involved. 2. A level of
maintenance in which lower ordinal numbers refer
to less-critical tasks, and higher ordinal numbers
refer to tasks requiring progressively higher
skills and technological expertise.
echelon grating A diffraction grating with extremely
high resolution. Generally useful only
over a small range of wavelengths.
echo 1. A signal that is reflected back to the point
of origin. 2. A reflected or delayed signal component
that arrives at a given point behind the main
component. 3. A radar blip, indicating an object
or thundershower. 4. Reflection of the signal on a
telephone line, caused by improper impedance
matching, or by overload of the system by too
many subscribers attempting to use the system
at the same time. 5. In audio systems, a circuit
that causes sounds to repeat one or more times,
at intervals ranging from a fraction of a second to
several seconds. 6. The effect produced by a circuit,
as defined in 5.
X
Long path (echo)
Earth
Short path
Y
echo
Ionosphere