Parts Express - Tech Terms Glossary

Tech Terms Glossary

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S/N (Signal to noise) Ratio: The proportion of true signal information to extraneous noise or interference that an audio or video unit delivers, usually expressed in decibels (dB). A higher number indicates a better S/N ratio. Measure of noise levels of a video signal: the higher the number the better.

Santoprene: Polymer (plastic) material that has similar weathering, flexibility and compliance to butyl rubber, but has lower recoil tendency (springiness) which can add unneeded resonances.

Satellite Speakers: Commonly used in home stereo systems along with a subwoofer. The subwoofer handles low frequencies up to 80-150 Hz, then the satellites take over and extend toward 20-30 kHz. This type of system eliminates the need for much larger speaker pairs that reproduce all of these frequencies, yet take up more room and are harder to hide in a room's decor.

Saturation (color): The vividness of a color. It is directly related to the amplitude of the chrominance signal.

Scanning: The rapid movement of the election beam in a pickup device of a camera or in the CRT of a television receiver. It is formatted in a line-for-line manner across the photo sensitive surface which produces or reproduces the video picture. When referred to a video surveillance field, it is the panning or the horizontal camera motion.

Sd: The measured surface area of a speaker's piston.

Secondary Cell: A cell that can be recharged to its voltage rating by causing current to flow in reverse polarity, from positive to negative regions. Examples: Nickel-Cadmium (Ni-Cd), Nickel-Metal Hydride (NiMH), Litium Ion (Li-Ion) and lead-acid cells and batteries.

Semi-automatic Turntable: A turntable designed to automatically return the tone arm to the rest when it reaches the lead-out groove on the record.

Sens: The reference sensitivity of a loudspeaker measured at one meter as a sound pressure level. It was originally measured while driving a speaker with one watt, but is also measured driving a speaker with a constant 2.83 volts AC.

Sensitivity: (optical pickup device) The amount of current developed per unit of incident light. It can be measured in watts with the projection of an unfiltered incandescent source of light at 2870 K degrees to the pickup device surface area. It can be then expressed in footcandles.

Servo Motor: A motor with a built-in automatic speed control device to stabilize motor rotation. Shadow bar across the screen or as a tearing in the top corner of a picture.

Signal-To-Noise Ratio (S/N): The proportion of true signal information to extraneous noise or interference that an audio or video unit delivers, usually expressed in decibels (dB). A higher number indicates a better S/N ratio.

Simplex (multiplexer): A multiplexer that allows the user to look at multi-screen images or perform time multiplex recording. It cannot record multiplexer pictures while showing multi-screen pictures.

SIP (Single In-line Package): A semiconductor design that consists of one row of pins.

Skating Force: Force drawing the tone arm toward the center when playing a record.

SPL (Sound Pressure Level): The measured loudness of a sound. Often measured in decibels (dB) from one meter (1m) away from a speaker driver while it is playing a test tone that is being driven by one watt (1W) of power from the amplifier. (Example: 92 dB 1W/1m) Also measured from a speaker that is being driven with 2.83 volts of audio voltage. (Example: 92 dB 2.83V/1m)

Spot Filter: A small insert used in a lens to increase the f-stop range of the lens.

S-shaped Tone Arm: A tone arm shaped in a S-shape as opposed to a straight tone arm.

Stylus: Needle-like object that follows the record groove and picks up vibrations.

Subwoofer: A speaker designed to deliver extremely low-frequency sound (usually below 100 Hz). An active powered subwoofer utilizes its own built-in amplifier, separate from the amp used by other speakers in a system, for cleaner, more powerful bass response. Active subwoofers have built-in crossover circuitry to filter the low-frequency signal.

Super VHS (Super Video Home System): A new format of high resolution VHS video recorders, capable of giving greatly improved picture if all features and special tapes are used. VHS compatible.

Surge Suppressor/Protector: component used to protect equipment that is sensitive to voltage variations (audio and computer equipment). Most often, suppressors/protectors will shut down completely at the introduction of a strong surge of power.

S-Video Input / Output: Special connectors that provide a sharper, higher-resolution picture by processing luminance and color signals separately to avoid interference. Available on high-resolution video sources, such as Hi8, ED Beta®, S-VHS VCRs, AV Laser players, DSS Digital Satellite System, and on selected "direct- view" and projection TVs.

Sync: Electronic pulses that are inserted in the video signal for the purpose of assembling the picture information in the correct position.