Hi! I'm new to the forums here, so please let me know if my etiquette is wrong :)  I've had an interest in telecommunications just about forever so this thing peaked my curiosity, and I couldn't find any explanations anywhere for it so I thought this forum would be a good place to start.

I stumbled across an unusual telephone number "prefix" I guess it would be called, and was wondering if anyone (possibly someone who has experience in this?) could explain what's going on?  

Just out of curiosity, I dialed an old number of a house I used to live at, which got disconnected when we left.  Usually I had only dialed this without the 09 area code, and it would answer with an automated message, "You have called 0, 9, 4, 1, 2,..... this number is not currently active", however today I tried dialing it with the area code 09 in front and it read out a completely different number: "You have called 0, 8, 3, 4, 9, 6, 9, 4, 1, 2,........." ..........that had me really confused. 

What could the number 083496 have to do with anything? (the number 9 between that and the phone number turns out to be the area code)

So as an experiment I tried dialing some numbers but adding this number to the front.  (EG for the number 09-123-4567 you would dial 083496-9-123-4567)  And it turns out that you can put that number before any phone number, from any phone or mobile (this includes cellphones, EG 08346-21-123-4567) and it will work...  Note that it takes around 15 seconds to start dialing, with a lot of "pops" and other sounds suggesting connections being made.

So what's going on?  Is my call being routed though a particular exchange?  Is it being measured somehow?  Applying some unknown significance?  08346 is a fairly random number (I'm guessing) so are there more of these "mystery" numbers, and do they mean anything?

Sorry for the huge amount of questions but I find this really fascinating - your answers are much appreciated :)