Signal square

A signal square is an aerodrome equipment internationally defined at the annex 14 of the Convention on International Civil Aviation by the International Civil Aviation Organization. It contains ground symbols to indicate visually the conditions on the aerodrome to over-flying aircraft. There are four basic signals.

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  A horizontal red square panel with yellow diagonals when displayed in a signal area indicates that landings are prohibited and that the prohibition is liable to be prolonged.
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  A horizontal red square panel with one yellow diagonal when displayed in a signal area indicates that owing to the bad state of the manoeuvring area, or for any other reason, special precautions must be observed in approaching to land or in landing.
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  A horizontal white dumb-bell when displayed in a signal area indicates that aircraft are required to land, take off and taxi on runways and taxiways only.
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  The horizontal white dumb-bell but with a black bar placed perpendicular to the shaft across each circular portion of the dumb-bell when displayed in a signal area indicates that aircraft are required to land and take off on runways only, but other manoeuvres need not be confined to runways and taxiways.
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  The landing T, showing the wind direction on an all-over landing field with the tail of the T pointing downwind. On airfields with runways it indicates the landing and take-off direction.
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  The right hand circuit indicator.
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  Air traffic services reporting office.
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  Closed runways or taxiways.
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  Directions for landing or take off, runway in use.
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  Glider flights in operation.