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SOLENOID—An electromagnetic device that changes electrical energy into mechanical motion; based
upon the attraction of a movable iron plunger to the core of an electromagnet [3].
SOLID—One of the three states of matter; it has definite volume and shape (ice is a solid) [1].
SOLID-STATE DEVICE—An electronic device that operates by the movement of elections within a solid
piece of semiconductor material [7].
SONIC—Pertaining to sounds capable of being heard by the human ear [10].
SOURCE—(1) The object that produces the waves or disturbance. (2) The name given to them end of a
two-wire transmission line that is connected to a source [10]. (3) The device which furnishes the
electrical energy used by a load [1].
SOURCE, MAINTENANCE, AND RECOVERABILITY CODE (SM & R CODE)—Specifies
maintenance level for repair of components or assemblies [14].
SPACE—Absence of an RF signal in cw keying. Key-open condition or lack of data in communications
systems. Also a period of no signal [12].
SPACE CHARGE—An electrical charge distributed throughout a volume or space [6].
SPACE DIVERSITY—Reception of radio waves by two or more antennas spaced some distance apart
[10].
SPACE WAVE—Radio waves that travel directly from the transmitter to the receiver and remain in the
troposphere [10].
SPACING—The condition in teletypewriter operation where a circuit is open and no current flows [17].
SPARK-GAP MODULATOR—A modulator that consists of a circuit for storing energy, a circuit for
rapidly discharging the storage circuit (spark gap), a pulse transformer, and a power source [12].
SPECIAL PURPOSE ELECTRONIC TEST EQUIPMENT (SPETE)—Test equipment that is
specifically designed to generate, modify, or measure a range of electronic functions of a specific or
peculiar nature on a single system or equipment [16].
SPECIFIC GRAVITY—The ratio between the density of a substance and that of pure water at a given
temperature [1].
SPECIFIC RESISTANCE—The resistance measured in ohms of a unit volume of a substance to the flow
of electric current. (The unit volume used is generally the circular mil-foot.) [4]
SPECTRUM—(1) The entire range of electromagnetic waves arranged in order of their frequencies. (2)
The range of frequencies considered in a system [10].
SPECTRUM ANALYSIS—The display of electromagnetic energy arranged according to wavelength or
frequency [12].
SPECTRUM ANALYZER—A test instrument that provides a visual display of the frequency distribution
of an RF signal such as a transmitter output [18].
SPIN VECTOR—In a gyro, a vector representing the angular velocity of the gyro rotor. The spin vector
lies along the spin axis of the rotor [15].
