Surface Mounting (SMT):

A method of soldering packages directly onto the surface of printed-circuit boards without insertion of the leads through hole in the board.

VAC:

Voltage, alternating current (see AC)

Switch Abbreviations:

SPST: Single-pole single-throw; SPDT: Single-pole double-throw; DPST: Double-pole single-throw; DPDT: Double-pole double-throw. (See also Forms). Please refer to the ITW Switches Characteristics/Circuits for more detail

VDC:

Voltage, direct current (see DC)
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