You can distinguish between internal and external calls simply by reading the display. Yes, you can change your ringtone like on the 9608 however that ring tone will apply to any inbound call.
The only alternative is to set a unique ring tone for the hunt group. This only works with certain handset models too.
First step is to go to System | Telephony | Ring tones
under 'ring tone plan' select one of the classic ring tone options and give it a name (You can set others up using this same method later)
Second step is to visit Group | Group and select the name of the ring tone you used above under 'Ring tone override'
Save & merge settings.
Important: Again, this will only work with certain handsets: 1400 Digital handsets, 9500 Digital handsets or J Series SIP (Except J129). It won't work on the 9611G.
I've tested this with the J series SIP Handsets and it works.
Thanks, Tim
Adelaide, Australia