Whenever maintenance work is required to be done on the Overhead Equipment{OHE},The power is switched off in the concerned section.Whenever the OHE is rendered dead in such a manner the procedure is known as a Power Block.Power Blocks are required to be...

Whenever maintenance work is required to be done on the Overhead Equipment{OHE},The power is switched off in the concerned section.Whenever the OHE is rendered dead in such a manner the procedure is known as a Power Block.Power Blocks are required to be taken with the prior permission of the Traction Power Controller,Section Controller and the concerned Station Master in whose area the Power Block is to be taken.However,the sections adjoining the Power Block Section are kept energised to ensure that the movement of trains is least affected.As such to ensure that the Maintenance Personnel do not inadvertantly enter the Live Catenary area,boards such as the above are provided to ensure that no one strays beyond the Working Limit.

The Hindi letters say "Vidyut Shakti Block" - Electric Power Block and also "Karya Seema" - Work Limits it seems that this may be the limit for electrified track. Perhaps this is a notice to the electric loco should not cross this point.