Linking PBXs

[dafault]

Both the main and remote offices have PBXs and these offices are connected utilizing a T1. Keeping the existing dial plan I want the ability for extension-to-extension dialing. What analog router voice modules would be best for each router, FXS or FXO and why?

[ebreniz]

I think MFT1 is the best option.

Which can be used to carry data and voice.

http://www.cisco.com/en/US/products/hw/routers/ps259/products_data_sheet09186a0080091b9c.html