1.0 link Rainbow Dash Network http://rainbowdash.net/ Bit Shift (bitshift) http://rainbowdash.net/bitshift http://rainbowdash.net/notice/1964429 @<span class="vcard"><a href="http://rainbowdash.net/user/5768" class="url" title="Thomas H"><span class="fn nickname">nlghtmaremoon</span></a></span> From some research the same subject prompted me to do: it's called a carrier signal flag, and it's meant to be flipped up both by you when you want to send something, and by the postal carrier when you've received something. I have no idea if it's actually still used like that, though, since I don't even live in the US.