I guess it could happen either way. It may be that when you register for their service that an 0870 number is assigned to your extension, however, most institutions that I have seen have the extensions already assigned to an 0870 number that relates in some way to the extension number but often not in an obvious way. In this case the room 0870 number remains constant if activated. It is likely just an assignment in groups to the physical location of the extensions. However the geographical number is often more closely related to the extension number (usually the last 3 or four digits are the same) Sometimes the first digit or two is only used internally to route an extension to extension call and these are replaced by part of the geographical code, sometimes not. But once one extension and its associated numbers are found similar numbers are relatively easy to deduce.

Sometimes the institution publishes an internal extension number and external number together eg for a porter's office in which case trying the same code can yield results if the internal number is similar to the one you require. Otherwise I guess we just have to work our way through all the registered area codes

You could try asking at one of the administration desks eg main reception or accomodation office if they can ring an extension for you to reach someone "whose internal number you know - but not their 0870 number" It might just show if it can be done across the unversity system and might reveal another part of the number. 

Student Union might know if someone has already cracked the problem - there is often at least one practical joker on the union that lives to subvert the system and gathers such information. The price of a pint or a curry usually worked to find it out.

nuff wrote on Nov 13^th, 2007 at 5:48pm:


I'm not sure that would work - my room is right next to Reception and they know me, they'd want to know why I can't use my own phone.

0161 295 **** is the prefix for 5**** extensions, which is the University system.
I've tried putting my extension into 0161 832 ****, and it rang, but my phone didn't.

I haven't had a chance to try the pre-2000 numbers yet. I will when I get time.

nuff wrote on Nov 13^th, 2007 at 10:40pm:


Ahh, I see what you mean. I'll try that.

nuff wrote on Nov 13^th, 2007 at 10:40pm:


No luck on any of those - some ring, but none of them ring here.

I've got a friend at Sheffield who was issued with a geographic number for her room... 

The accommodation here is owned by the University, but the phone lines, handsets and such are all provided by Keycom. That's why I'm not sure about it working. I'll see what I can find out though.

Renewed thanks for everyone's help and suggestions - much appreciated.

jgxenite wrote on Nov 14^th, 2007 at 5:48pm:

She was in Tapton last year, and was definitely given an 0114 number - I've just checked with her!

jgxenite wrote on Nov 14^th, 2007 at 5:48pm:

No official communication comes through the phones, it's all done by e-mail. They wouldn't be able to rely on using phones to contact everyone, as not everyone has the phones plugged in and registered. (As far as I know, there's only me and one other person in this house who've done so - and there are 12 of us here.) I will give it a try, though.

jgxenite wrote on Nov 14^th, 2007 at 6:28pm:


I know someone now in Ranmoor at Sheffield (jgxenite and I were discussing it in another topic) and they were only given the 0870 number (it was on the phone when they got there) No-one bothers with the phone because they all use mobiles, but finding the geographical number is saving us a fortune. (Thanks to this website!)  Their extensions are 5 xx xx  and are reached by 0114 21 5 xx xx  . You can now find it on the list under University of Sheffield.



If we can find another digit used before 1xxx for the manchester accomodation it might be worth trying codes than end with that digit before trying the rest.