Different rings from internal and external calls

Hello to all , I will first describe the situation .
FreePBX it is connected to a Patton sn4120 with 2 BRI , 4 SIP phones connected to the PBX and 22 analog phones connected to the PBX via a grandstream gxw4200 fxs gateway .
The calls come at a Ringroup doing play 7 phones simultaneously ( 3 sip and 4 analog and 1 cordless ) .
That's it in terms of configuration and it works fine . What the customer asks me ( with the old analog exchange that I replaced it worked) is diversifying the sound of the 6 internal Ringroup depending on whether the call comes from outside or inside .
The models of phones are
3 Grandstream gxp1610
3 ST - 200 ( analog )
1 Brondi Cruise ( cordless )
I do not know why but it seems that this feature to the customer is vital

Thanks in advance