I have a number of linksys sip phones (941 and 942) and multiple telephone numbers. Is it possible to have the phones ring differently for each number?
This would be done with the Alert Info field of your inbound route, it will pass the alert info you put in that field to the phones. Search around and see if your phones support the alert info, they should being linksys.
The alert info is what I already found, but can’t seem to find it within my phones 
It does however have this section:
Are you trying to use custom uploaded files or just the built in ones with a different ring tone for each number?
Using the built in ring tones is possible, uploading your own is not.
http://community.freepbx.org/t/changing-ringtones-on-cisco-spa504g/16511/2
I want to use default ringtones. Let’s say my alert info fields in FreePBX are “number1” and “number2”, do I need to add the following to the Cadence 1 and Cadence 2 fields?
;number1:Simple-1
;number2:Simple-2
No, assuming that the ring tone settings are still at the defaults in your phone, I think you need to put Simple-1 in the alert info field of your inbound route.
So wait, I have to set this from freepbx and not from the phone?
I believe so, I don’t have your phones to test, but from what I can tell from the other thread I copied, leave your phone the way it is and in your inbound routes change the alert info to Simple-1 Simple-2 etc to get different ringtones. To see the whole list of alert infos you can use, look at the names in the ringtones menu option in the phone.
Have tried a lot of combinations, but can’t seem to get this to work, the phone keeps using the ringtone that is set. Ideas are welcome.