But what happens when you dial it? Well, this...

The live action trailer released earlier today for The Bureau: XCOM Declassified contains a number of Easter Eggs - including an active phone number.

The track that plays is identical to the one in the trailer, before fading into what sounds like a siren. But is there a hidden message in there somewhere? We're not too sure. We've tried slowing it down, playing the track in reverse and performing all kinds of technical wizardry, but we're stumped.

If you can figure out what it's all about, let us know in the comments below.

And if you want to hear it for yourself, give the number a call: 415-507-7616. Be aware if you're dialling from outside the US, though. It's a Californian number, so you'll probably be charged for an international call.

The phone number wasn't the only thing hidden in The Bureau's live action trailer, though. Did you spot the hidden Sectoid...?