You simply configure both OBi's with:
Voice Services -> OBiTALK Service -> InboundCallRoute:
{(Mcot)>(Mpli):pli},{(Mcot)>(<*1:>(Msp1)):sp1},{(Mcot)>(<*2:>(Msp2)):sp2},{(Mcot)>(<*8:>(Mli)):li},
{(Mcot)>(<*9:>(Mpp)):pp},{(Mcot)>(<**1:>(Msp1)):sp1},{(Mcot)>(<**2:>(Msp2)):sp2},
{(Mcot)>(<**8:>(Mli)):li},{(Mcot)>(<**9:>(Mpp)):pp},{(Mcot):aa},{ph}
Note: Replace pli above (2 places) with the OBi's PHONE Port -> PrimaryLine trunk name (sp1,sp2,li,pp,tg1) as the OBi won't do it for you.
User Settings -> User Defined Digit Maps -> User Defined Digit MapX:
Label : cot
DigitMap : (200123456|200123457)
where 200123456 is the OBiTALK number for OBi #2 and 200123457 is the OBiTALK number for OBi #3.
Note: These are trusted caller OBiTALK numbers. This DigitMap should also contain the OBiTALK numbers of any OBiON Apps that are used.
In the PHONE Port and Auto Attendant DigitMap's, change [1-9]x?*(Mpli) to [1-9]x?*@@.
In the PHONE Port and Auto Attendant OutboundCallRoute's, change {([1-9]x?*(Mpli)):pp} to {([1-9]x?*@@.):pp}
Speed Dial #2 : PP(ob200123456)
Speed Dial #3 : PP(ob200123457)
where 200123456 is the OBiTALK number for OBi #2 and 200123457 is the OBiTALK number for OBi #3.
From either OBi, you make calls though the local OBi dialing normally:
18005551212 -> Local PrimaryLine
**1 18005551212 -> Local SP1 Service
**2 18005551212 -> Local SP2 Service
**8 18005551212 -> Local LINE Port
**9 200123456 -> Local OBiTALK Service
From OBi #3, you make calls through OBi #2 by dialing:
2*18005551212 -> OBi #2 PrimaryLine
2 **1 18005551212 -> OBi #2 SP1 Service
2 **2 18005551212 -> OBi #2 SP2 Service
2 **8 18005551212 -> OBi #2 LINE Port
2 **9 200123456 -> OBi #2 OBiTALK Service
From OBi #2, you make calls through OBi #3 by dialing:
3*18005551212 -> OBi #3 PrimaryLine
3 **1 18005551212 -> OBi #3 SP1 Service
3 **2 18005551212 -> OBi #3 SP2 Service
3 **8 18005551212 -> OBi #3 LINE Port
3 **9 200123456 -> OBi #3 OBiTALK Service
If you'd like the other OBi's phone to ring on incoming calls (no Sipgate or Google Voice forwarding required):
For the trunk(s) you wish to ring the other OBi:
Voice Services -> SP1 Service -> InboundCallRoute
Voice Services -> SP2 Service -> InboundCallRoute
Voice Services -> OBiTALK Service -> InboundCallRoute
Physical Interfaces -> LINE Port -> InboundCallRoute
change ph or {ph} to {ph,PP(ob290123456)}
where 290123456 is the OBiTALK number of the other OBi.