Vertical Tray Flame Test -- UL and IEEE test criteria for resistance to flame propagation of conductors or cables; employs a 70,000 BTU/hr flame source applied to the test specimen installed in a vertical cable.

VHF -- Very high frequency. The spectrum extending from 30 to 300 mHz as designated by the Federal Communications Commission.

Video -- Pertaining to picture information in a television system.

Video Pair Cable -- A transmission cable containing low-loss pairs with an impedance of 125 ohms. Used for TV pick-ups, closed circuit TV, telephone carrier circuits, etc.

Viscosity -- A measure of the resistance of a fluid to flow (usually through a specific orifice).

VLF -- Very low frequency. The spectrum extending from 10 to 30 kHz as designated by the Federal Communications Commission.

VN-TC -- Brand-Rex tradename for its 90°C, 600 volt power and control cable designed for use in continuous rigid cable supports and in raceways.

Volt -- A unit of electrical pressure. One volt is the electrical pressure that will cause one ampere of current to flow through one ohm of resistance.

Voltage -- Electrical potential or electromotive force expressed in volts.

Voltage Breakdown -- Test to determine maximum voltage of insulated wire before electrical current leakage through insulation.

Voltage Drop -- The voltage developed across a component of conductor by the current flow through the resistance or impedance of the component or conductor.

Voltage Levels -- Power limited: 0 to 300 volts; low voltage: 600 to 2000 volts; medium voltage: 5000 to 69,000 volts.

Voltage Standing Wave Ratio -- The ratio of the maximum effective voltage to the minimum effective voltage measured along the length of a mismatched radio frequency transmission line.

Volume Resistivity (Specific Insulation Resistance) -- The electrical resistance between opposite faces of a 1 cm cube of insulating material, commonly expressed in ohms/cm.

Vulcanization -- A chemical reaction in which the physical properties of an elastomer are changed by reacting it with sulfur or other cross-linking agents.

VW-1 -- A vertical flame test designation applying to single conductor low voltage wires only. It is a modification of the standard industry vertical flame test using a tirrill burner, with restrictions having been added regarding reapplication of the burner until all flaming from the previous application self-extinguishes. Also cotton batting is placed beneath the specimen to check for dripping, flaming particles. The test specimen is usually a size 14 AWG wire rated 600 volts.