Tip: to find a specific term, use the Acrobat search : click
on the binocular icon in the window bar menu

Virtual Circuit A logical relationship between two users of the X.25 service. Virtual Circuit Priority The priority associated with a connection (virtual circuit) which is established between two systems prior to the transmission of data. Visibility The ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night. Vision The main conceptual mental picture containing the very broadest of guidelines as to where the project, programme or company is going and how is likely to get there and how it will recognise when it has arrived there. Visit Occasion to experience an operational environment. Visual Aids Aids to communication which utilise the sense of sight (such as computer-based presentation, slides, overheads or view foils, mock-up, models posters). Visual Flight Rules Under clear weather conditions (VMC) aircraft are allowed to fly using visual navigation. Most small aircraft use visual navigation as they do not have proper equipment to permit IFR navigation. Visual Flight Rules Flight A flight conducted in accordance with the visual flight rules. Visual Meteorological Conditions Meteorological conditions under which there is sufficient outside view to enable visual aircraft control and navigation (VFR flights).
See also Instrument Meteorological Conditions. Voltage Controlled Oscillator Oscillator whose frequency is adjusted by a voltage.
W
Waiver A written authorisation to accept an item which, during manufacture or after having been submitted for inspection, is found to depart from specified requirements, but nevertheless is considered suitable for use "as is" or after repair by an approved method. Warning An annunciation that is generated when immediate recognition and corrective or compensatory action is required; the associated colour is red. Warning time (SNET) The amount of time between a Safety Net alert and the conflict (SNET), terrain collision hazard or imminent airspace penetration. Way-point A specified geographical location used to define an area navigation route or the flight path of an aircraft employing area navigation. Sometimes also called route point or RP.