ROTOR(1) The revolving part of a rotating electrical machine. The rotor may be either the field or the
armature, depending on the design of the machine . (2) The rotating member of a synchro that
consists of one or more coils of wire wound on a laminated core. Depending on the type of synchro, the
rotor functions similarly to the primary or secondary winding of a transformer .
RPKThe symbol used to represent the resistance between the cathode and plate of a tube .
RUNNING OPENThe teletypewriter condition where the type hammer constantly strikes the type box
but does not print or move across the page .
SATELLITE ECLIPSEAn eclipse where the rays of the sun do not reach the satellite. This prevents
recharging of the solar cells of the satellite and decreases the power to the transmitter .
SATELLITE-SUN CONJUNCTIONA period when the satellite and sun are close together and the noise
from the sun prevents or hampers communications .
SATURABLE-CORE REACTORA coil in which the reactance is controlled by changing the
permeability of the core .
SATURATION(1) The condition existing in any circuit in which an increase in the input signal produces
no further change in the output . (2) The operating point of a vacuum tube or transistor at which a
further increase in grid or base current no longer produces an increase in plate or collector current 
. (3) In a magnetic core, the condition in which a magnetic material has reached a maximum flux
density and the permeability has decreased to a value of (approximately) 1 .
SCALING FACTORThe term used to describe the use of unequal resistors in a servo's summing
network to compensate for differences between input and output signal levels .
SCANNING(1) The process of subdividing a picture in an orderly manner into segments. This is used in
facsimile transmission . (2) Systematic movement of a radar beam to cover a definite pattern or area
in space .
SCAT CODEA four-digit subcategory code used to identify the functional measurement parameters that
can be satisfied by any one of many pieces of test equipment .
SCATTER ANGLEThe angle at which the receiving antenna must be aimed to capture the scattered
energy of tropospheric scatter .
SCHEMATICA diagram which shows, by means of graphic symbols, the electrical connections and
functions of a specific circuit arrangement  .
SCHEMATIC SYMBOLSA letter, abbreviation, or design used to represent specific characteristics or
components on a schematic diagram .
SCINTILLATIONApparent change in target reflectivity. Motion of the target causes successive radar
pulses to bounce off different parts of the target, such as fuselage and wingtip .
SCREEN GRIDA grid placed between a control grid and the plate and usually maintained at a fixed
positive potential .
SCREENINGProcess of applying nonconductive or semiconductive materials to a substrate to form thick
film components .