Below is my recommended configuration.
I did not test any of this and hopefully I didn't make any mistakes.
OBi202
Service Providers -> ITSP Profile A SIP -> ProxyServer: 127.0.0.1
Service Providers -> ITSP Profile A General -> DigitMap:
(1xxxxxxxxxx|<1>[2-9]xxxxxxxxx|011xx.|0|XX.S3)
Voice Services -> SP1 Service -> AuthUserName: OBi202
Voice Services -> SP1 Service -> X_RegisterEnable: unchecked
Voice Services -> SP1 Service -> X_InboundCallRoute:
{OBi110b:ph2},{ph}
Physical Interfaces -> Phone1 Port -> OutboundCallRoute:
{(<#:>):ph2},{(XX.):sp1($1@aa.aa.aa.aa:5060)}
Physical Interfaces -> Phone2 Port -> OutboundCallRoute:
{(<#:>):ph},{(XX.):sp1($1@bb.bb.bb.bb:5060)}
OBi110a
Service Providers -> ITSP Profile A SIP -> ProxyServer:
cc.cc.cc.ccService Providers -> ITSP Profile A SIP -> X_SpoofCallerID: Checked
Voice Services -> SP1 Service -> AuthUserName: OBi110a
Voice Services -> SP1 Service -> X_RegisterEnable: unchecked
Voice Services -> SP1 Service -> X_InboundCallRoute:
{>(<0:>):li},{li}
Physical Interfaces -> Line Port -> InboundCallRoute: sp1(0)
OBi110b
Service Providers -> ITSP Profile A SIP -> ProxyServer:
cc.cc.cc.ccService Providers -> ITSP Profile A SIP -> X_SpoofCallerID: Checked
Voice Services -> SP1 Service -> AuthUserName: OBi110b
Voice Services -> SP1 Service -> X_RegisterEnable: unchecked
Voice Services -> SP1 Service -> X_InboundCallRoute:
{>(<0:>):li},{li}
Physical Interfaces -> Line Port -> InboundCallRoute: sp1(0)
aa.aa.aa.aa is the IP address of OBi110a
bb.bb.bb.bb is the IP address of OBi110b
cc.cc.cc.cc is the IP address of OBi202
OBi202 Phone1 port will route outbound calls to OBi110a
OBi202 Phone2 port will route outbound calls to OBi110b
Dial "0" to get dial tone on the respective OBi110 PSTN line
Any other number will be routed out the PSTN line.
Inbound calls on OBi110a will be routed to OBi202 Phone1
Inbound calls on OBi110b will be routed to OBi202 Phone2
Dial # on either OBi202 phone port to ring other phone port