edgekaos wrote:
I"m trying to wire two dual 40w fluorescent light fixture in parallel
in a signal circuit and without success. Each fixture has two 40w tubes
and an electrical ballast. If I wire each one separatly then it'll
work. I gather the reason might be interference between the two
ballasts but I want to hear some expert opinon.

Shouldn't be any interference... After all, technically all the
fluorescent lamps in your house are in parallel. Heck, all the
fluorescent lamps in your part of town are technically in parallel
across the local transformer.