Wizard Radar?

[Olivia]

No: HPFGUIDX 43289

I've been reading through the list archives which is a fascinating but
time-consuming process and it reminded me to pose a question that I've been
wondering about for awhile. It's been sometime since I've reread the books;
I've only just taken Sorcerer's Stone off the shelf yesterday to begin
again, but I can't remember this being directly addressed at any point...

Is there such a thing as wizard radar? Can one wizard tell another just by
looking at him? Not taking into account obvious give-aways suchas robes,
wands, bad attempts at Muggle dress, Harry's scar, Dumbledore's hair/beard,
Mad-Eye's magical eye, etc. Is there anyway for them to instantly recognize
another wizard? And vice-versa? Could a wizard spot a Muggle in Wizard
robes?

For example, say there are three men in a room all dressed in ordinary,
everyday Muggle clothes. Man A and B are wizards. Man C is a Muggle. Would
Man A and B recognize each other? Would Man A and/or B recognize that Man C
is just a Muggle?

As I said, I haven't come across this yet. If someone has or it's been
discussed, please do point me in the right direction.

Olivia