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form of modulation (including time of arrival and spacing of pulses).

The flexible and comprehensive nature of electronic methods is thus indicated.

The end point of the channel involves the [[underline]] presentation [[/underline]] of information and its use. The desirable form of presentation differ as different stages in the flight and are governed by the limitations of the pilot in assimilating the required information. The quantity and precision of the required information, and the speed with which it must be translated into action, are greatest at the terminals of the mission, i.e., approach, landing, bombing run, etc. During en route cruising, the situation is less critical but the possibility of fatigue and the introduction of excessive deviations must be recognized. [[strikethrough]] Moreover, the [[/strikethrough]] information may be introduced directly to automatic flight control instruments, and in this case, the presentation is used simply for monitoring. [[underline in pen]] One of the most important requirements of any indicator or presentation device is that it must in no circumstances provide false information without the pilot's knowledge. [[/underline in pen]]

Presentation devices may be classified according to precision and quantity of information they present. The most primitive is the simple warning device (signal lamp, flag indicator, horn) which indicates merely that some pre-determined limit has been exceeded. The next in order is the deviation device (left-right pointer, A-H coding, etc.) which indicates deviation from a prescribed value, but does not indicate precisely the extent of the deviation. This type of indicator requires continuous attention and tends to cause fatigue on prolonged use. The third category is the quantitative indicator, that is, one calibrated in numbers. The indicated quantity is used, with reference to the prescribed value to set courses, for example, and to correct deviation. Often such numerical indications require mental or mechanical to [[transposed bo]][[tain the operating instruction. A basic advantage of quantitative indication is the ability to determine,

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