This is only a guess, be sure to wait for confirmation before using. My dictionaries and the net do not give any direct electric engineering translation. Normal dictionaries show "a wrench / spanner in the works" for "Querschuss" and there are several net references to the term in this sense.

This site uses the term for computer voltage fluctuation protection but I do not think they mean it in an electrical engineering sense.

"Ein Querschuss kann Tausende kosten"

http://www.lau-net.de/WDI/fsu_usv.htm

Perhaps a "jump spark" = "Überschlagsfunke" is meant where the voltage is high enough to jump through the air over an open or switch in the circuit. As per Ernst and this site:

http://www.connect.ab.ca/~barachj/car-dicj.htm

Dan

This is the meaning. It is different from a "Kurzschluss" in that is not a short circuit beteen the live wire and ANY other part, meant is ONLY the short circuit between the two lead wires. Refer to web page below for an illustration. I'm not sure if there's a short English term for that.

I admit I'm not a specialist on electric wiring but I found above term for Querschluss in my Dictionary of Electronics, Communications and Electrical Engineering. There was no additional info- maybe someone more knowledgable can confirm? I believe it means that the switch is to tbe switched to Emergency(Not)- danger of short circuit. Good luck!