Electrified Cable Overhead Road Post Mounted Sign - 779 R2/RA2 (Face Only)The electric symbol road sign diagram 779 is used where a road passes under an electrified overhead power cable. This usually refers to where overhead tram or railway cables cross over a level crossing and should be used wherever this happens. This warning sign should always be accompanied by a plate indicating the largest safe height for a vehicle to pass under shown in imperial and metric units. The supplementary plates to do this can be found in