I GOT IT!!! I used the following settings but if you want to see from HW, the original poster, here's the link:
http://homecommunity.cisco.com/t5/VoIP-Adapters/Connect-back-to-back-2-SPA-3102/td-p/188833.
Just be sure to use the Internet port on the spa3102 and not the Ethernet port which was my mistake. and also add the default dial plan to dial plan #1 in the spa3102
Configure As Follows:
On the SPA3102 attached to the PSTN line.
PSTN Line Tab
Line Enable: YES
NAT Mapping Enable: yes or no depending on the router used
NAT Keep Alive Enable: yes or no depending on the router used
Register: No
Make Call Without Reg: Yes
Ans Call Without Reg: Yes
UserID: spaone
VoIP-To-PSTN Gateway Enable: yes
VoIP Caller Auth Method: none
VoIP Default DP: 2
VoIP Caller Default DP: none
none will give you the actual PSTN dial tone when the VoIP-to-PSTN gateway answers the call
PSTN-To-VoIP Gateway Enable: yes
PSTN Caller Auth Method: none
PSTN Ring Thru Line 1: no
PSTN Caller Default DP: 2
Dial Plan 2: (S0<:spatwo@ipaddress: 5060> )
The dial plan will automatically dial the distant SPA112 Line 1 when the PSTN-to-VoIP gateway answers the call
Where spatwo is the userid on the Line1 tab of the distant SPA112 (spatwo)
Where ipaddress is the ip address of the distant SPA112
Where 5060 is the sip port number of the Line 1 tab on the distant SPA112
VoIP Answer Delay: 0
PSTN Answer Delay: 2
Where 2 seconds is long enough to receive an incoming caller id on the pstn line (if you care about it)
Line-In-Use Voltage: 30
Where 30 is about half way between the on-hook and off-hook voltage of your pstn line (polarity disregarded)
Line 1 Tab
Enable IP Dialing: YES
On the Distant SPA112 Line 1 tab
Line Enable: Yes
NAT Mapping Enable: yes or no depending on your router
NAT Keep Alive Enable: yes or no depending on your router
Register: No
Make Call Without Reg: Yes
Ans Call Without Reg: Yes
UserID: spatwo
DialPlan: (S0<:spaone@ipaddress:5061> )
Where spaone is the useid on the pstn line tab of the SPA3102 attached to the pstn line
Where ipaddress is the ipaddress of the SPA3102 attached to the pstn line
Where 5061 is the sip port number on the pstn line tab on the SPA3102 attached to the pstn line
Enable IP Dialing: YES
Note: Depending on your network you may or may not have to have NAT Mapping Enable. If you do have NAT Mapping Enable you may also need to configure a STUN server depending on the router that you are using.
If the two ip addresses are not on the same local network you will need to forward the sip port in the router to the SPA3102 and you will need to use the external ip address.
