kindly give the exact model of quintum so that we can give you advise.
with your requirments you need the AXM series.
1. Between Quintum 1 & 2 can do call only by extension dial (i.e: when phone #1 from Quintum 1 being pickup and then phone #1 from Quintum #2 will automatically Ringing).
– you can do force route
via telnet you
config-LineCircuitRoutingGroup-1# frn 5551111.
the 5551111 is the assign number of your FxS
2. In Quintum 1, I plug channelbank to FXO port for GSM Call purpose.
-in this scenario you may assign HopoffNumberDirectory dialling pattern.
3. for PSTN calls, I plan to route to local VOIP provider.
-yes it can connect with VoIP Providers, but as mike says “there are many ways to do what you want, all depends on the specifics.”