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Unsupported Hold

A hole containing no conductive material nor any other type of reinforcement.

Underwriters’ Symbol

A logotype authorized for placement on a product which has been recognized (accepted) by Underwriters Laboratories, Inc. (UL).

Undercut

A groove or excavation at one edge of a conductor caused by etching.

Ultrasonic Soldering

Fluxless soldering wherein molten solder is vibrated at ultrasonic frequencies while making the joint.

UL

Underwriter’s Laboratories, Inc., a corporation for the purpose of establishing safety standards on types of equipment or components in USA and Canada.

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