Overhead wire marker

[Image:Wire_marker.jpg|thumb|A spherical marker. Spherical markers are also known as aerial marker balls.]
Overhead wire markers are safety instruments applied to the overhead power lines marking transmission lines and ropeways along the flight path during the day.
Image:Einebenenleitung.jpg|thumb|Markers on a line near an airfield Markers are often installed on overhead lines near airfields, or at river crossings where there is a possibility of seaplanes using the river. Some markers contain conductor marking lights or strobe lights to improve visibility at night or in fog.