The best vic card to get for any -to any comunication would be

E&M vic cards. The reason being e&M will allow calls to be made to or from both directions because it generates a dial-tone and collects digit dialed..

1. If you have a combination of fxo and remote fxs which is the other way

to go. The fxo would not generate a dial-tone hence we can not call

from the PBX to the remote extentions, but can call from the other side. The only way we can use this setup is to

trunk remote fxs to the local PBX. dial-tone will be produced by the local PBX

when the remote phone goes off-hook since we already have a trunk(active voice-path opened) to the

local PBX.

If the intention is to connect the two PBX's together in

such a way that extension dialed on remote end be forwarded to the remote PBX for further decision making and vise varsa, then use e&M-to-E&M

2. If the remote router would have analog phone connected to terminate the remote extension on

the router then trunk between fxs and local fxo.