daft question on LED indicators and high VDC

[irving2008]

Well a series resistor could be used.. 68-24 = 44v @ 20mA = 44/.02 = 2200ohm and 44 * .02 = 0.88W so need a 2200ohm, 2W resistor.
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Alternatively could use a 43v zener diode like this which might actually be cheaper since can be bought 1 off whereas resistors generally need to be bought 10 off. When using the zener the end with the band goes to the + side of the supply. Get it the wrong way round and both zener and LED will fry faster than you can say magic smoke!
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For heat dissipation purposes the zener should ideally be mounted on a bit of single sided circuit board approx. 60mm x 30mm. Make a single 2mm cut across the copper 40mm from one end to create two electrically separate areas. Form the leaas of the zener so it sits flat and solder the lead from the banded end to the larger area, keeping the lead full length. the body of the zener should just straddle the cut. Solder the other lead to the smaller area. If possible mount the board vertically to aid convection.