SL Sensitivity Level
S/L Sub-Level
Slant Range The line-of-sight distance from the aircraft to a DME
ground station.
SLEP Service Life Extension Program
SLM Standard Length Message
SLS Side-Lobe Suppression. A system that prevents a
transponder from replying to the side-lobe interroga-
tions of the SSR. Replying to side-lobe interrogations
would supply false replies to the ATC ground station
and obscure the aircraft location.
SLV Sync Lock Valve
SMC System Management and Communication
SMD Surface Mount Device
SMGCS Surface Movement Guidance and Control Systems
SMI Standard Message Identifiers
SMR Surface Movement Radar
SMSO Space and Missile Systems Organization
SMT (1) Aileron/Rudder Servo Mount
(2) Elevator Servo Mount
(3) Servo Mount
(4) Stabilizer Trim Servo Mount
(5) Station Management
SNR Signal-to-Noise Ratio
SOIT Satellite Operational Implementation Team
SOP Standard Operating Procedure
SOS Silicon On Sapphire
SPATE Special Purpose Automatic Test Equipment
SPC Statistical Process Control
SPD Speed
SPE Seller Purchased Equipment
Speed of Light Represented by the symbol c and has a value of 2.9979250 x 10 metres/second or 983,571,194 feet/second.
SPI Special Position Identification
SPIP Designation for a transponder ident pulse.
SPKR Speaker
SPM (1) Surface Position Monitor (2) Stabilizer Position Modules
Spoking Spoking refers to a display presentation which radi-ates outward from the display origin like the spokes on a wagon wheel.
SPR Sync Phase Reversal (term used in Mode S transpon-ders)
SPS Standard Positioning Service
SQ or Sql Squelch
Squall Line A squall line is a line of thunderstorms and develop-ing thunderstorms.
Squawk Reply to interrogation signal (XPD).
Squelch A control and/or circuit which reduces the gain in response of a receiver. The squelch is used to elimi-nate the output noise of the receiver when a signal is not being received.
Squitter (1) The random pulse pairs generated by the ground station as a filler signal. (2) The transmission of a specified reply format at a minimum rate without the need to be interrogated (filler pulses transmitted between interrogations) [XPD]. (3) Spontaneous Transmission generated once per sec-ond by transponders.
SR SwissAir
SRADD Software Requirements And Design Description
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