Switching calls between FXSs

Hi all, I have a simple setup in mind and I want to know your inputs on weather I would be able to make it work.

Current setup:
I have two FXSs one from Vonage and another from my local phone company. The original idea was to use SIP client on our cell phones so we can route calls from those two lines to our cell phones. The idea worked perfectly as I wanted my friends in the US who call me at their evening times to reach me here in Australia ( where I will be usually at work).

However, I have noticed that my new office has poor 3G connectivity and the SIP clients are always losing connectivity. So I am unable to receive calls from the two FXS lines. So I am thinking of the following setup.

New Setup I will continue using the two FXS lines, but when I get a call on the vonage line, Asterisk takes the call and uses the local line to call my cell phone and link the two together. And another addition is when I want to call international numbers, I call the local number from my cell phone or my desk phone at work, and press a 0 or an * or something, and Asterisk opens the Vonage line and connects me.

I know the language above is not strictly “Asterisk tech”, but I am still a rookie and getting my bearings right. Any help would be greatly appreciated. Thanks in advance.

If you’ve got a device from Vonage and you want to put that call back out on the PSTN, first check your local laws to make sure you’re not violating anything. If you’re good, then you’d need one FXO interface to receive the call from the FXS interface provided by the Vonage device, and another FXO interface to take a line from your Telco. Asterisk can then bridge everything together.