18WuD2x

612 scientific notation • seaborgium
Generally, the mantissa is greater than or
equal to 1, but less than 10; the power of 10 is adjusted
accordingly. Thus, for example, 203,700 =
2.037 × 10 5 ; 0.000533 = 5.33 × 10 –4 . See also
SIGNIFICANT FIGURES.
scintillating crystal A crystal, such as one of
sodium iodide, that sparkles or flashes when exposed
to radioactive particles or rays.
scintillation 1. In radar operations, the apparent
rapid displacement of a target from its mean position.
2. A momentary flash of light produced in
a phosphor or scintillating crystal when a highvelocity
particle strikes it. 3. A small fluctuation
in radio field intensity at a receiving point.
scintillation counter A radiation counter consisting
essentially of a scintillating crystal in combination
with a photomultiplier tube. Flashes from
the excited crystal cause the tube to deliver output
pulses that are totaled and indicated.
scintillator material A substance, such as crystalline
sodium iodide, that scintillates under certain
stimuli.
scissoring A method of interrupting the electron
beam in a cathode-ray tube when the beam
would not land on the phosphor screen.
SCLC Abbreviation of SPACE-CHARGE-LIMITED
CURRENT.
sco Abbreviation of SUBCARRIER OSCILLATOR.
scope Colloquialism for OSCILLOSCOPE.
Scott oscillator See PARALLEL-TEE OSCILLA-
TOR.
scp Abbreviation of SPHERICAL CANDLEPOWER.
SCR Abbreviation of SILICON-CONTROLLED REC-
TIFIER.
scrambled signal Any signal in which (for secrecy
or exclusivity) the elements are disarranged according
to an encryption algorithm. Thus, intelligent
reception is possible only if the signal is
processed via a suitable decryption algorithm.
Example: SCRAMBLED SPEECH.
scrambled speech Voice transmission in which
the frequencies have been inverted to prevent
eavesdropping. It is automatically unscrambled
(by reinversion) at the receiver to restore intelligibility.
scrambler circuit A circuit containing filters and
frequency inverters for scrambling speech.
scratch filter An audio-frequency low-pass filter
that suppresses high-frequency noise caused by
friction between a phonograph disc and the needle.
Input
scratch filter
Output
scratchpad memory In computers, a low-capacity
memory that stores an intermediate result of a
calculation.
scratch tape Magnetic data tape that can be overwritten
for any purpose.
screen 1. See SCREEN GRID. 2. See SHIELD.
3. The front surface of a cathode-ray tube. 4. The
surface of a computer or terminal display.
screen angle In radar, the angular difference between
the actual horizon and the plane perpendicular
to the line connecting the radar set with
the center of the earth.
screen current Symbol, I S or I SG . The current flowing
in the screen circuit of an electron tube.
screen grid In a vacuum tube, a grid element between
the control grid and plate. It reduces the
internal grid-plate capacitance, and consequently
prevents self-oscillation when the tube is used in
a straight-through amplifier.
screen-grid neutralization Neutralization of an
amplifier that uses a tetrode vacuum tube. Such
circuits require smaller neutralizing capacitances
than those used in triode amplifiers because
of the lower interelectrode capacitance of the
screen-grid tube.
screen illumination Edge lighting of the transparent
screen of an oscilloscope, to make the lines of
the graticule more clearly visible.
screen material See PHOSPHOR.
screen resistance Symbol, R S or R SG . The internal
resistance presented by the screen-grid/cathode
path of an electron tube.
screen room See CAGE.
screen voltage Symbol, E S or E SG . The voltage at
the screen grid of an electron tube.
scribing The etching of a semiconductor wafer to
facilitate breaking the wafer into smaller pieces.
ScriptX A high-level programming language used
in the writing of software for personal computers—especially
in multimedia. Developed by
Kaleida Laboratories.
SCS Abbreviation of SILICON-CONTROLLED
SWITCH.
SCT Abbreviation of SURFACE-CHARGE TRAN-
SISTOR.
S curve 1. The voltage-versus-current curve for a
negative-resistance device. Compare N CURVE.
2. The response curve for a frequency-modulation
discriminator or ratio detector.
SD Abbreviation of STANDARD DEVIATION.
S D band A section of the S BAND extending from
4200 to 5200 MHz.
SDF Abbreviation of static direction finder.
SDR See SOFTWARE-DEFINED RADIO.
Se Symbol for SELENIUM.
seaborgium Symbol, Sg. Also called unnilhexium
(Unh). Atomic number, 106. The most common
isotope has atomic weight 263. Classified as a
transition metal. It has a half-life on the order of
1 second or less, is human-made, and is not
known to occur in nature.