Don’t raise a flag telling your readers that you don’t know when to spell words like signaling (Or is it signalling?).

The doubling of the l when adding a suffix to a word tends to be a British convention. So, if you are in America, use signaled. If you’re in Britain, use signalled.

Other words this rule applies to includes:
AMERICAN: fueling, marveling, modeling, traveling
BRITISH: fuelling, marvelling, modelling, travelling

An exception in America is when the stress of the word falls on the second syllable. Then use a double l, as in: annulled, expelled, extolled, patrolled.

A few British spellings also stick with a single l, though they are few: appealed, devilish, loyalist, travelogue.