[cisco-voip] Setting up a constant voice link

[Greg Maiorana]

Hello All,
       Im trying to work out a solution with a customer to bring their 
current pots leased line system to a VoIP solution. The customer 
currently has a PSTN leased line from site A to B, which then plugs into 
some type of intercom system each end(think of an analog phone on each 
end with it off hook all the time).

Is there anyway to do this over VoIP ?
That is have an open link between say 2 x 1721 or 1751 cisco routers 
with FXS ports to have an non stop open stream between the FXS port at 
each location. So when customer A presses the intercom button to connect 
to site B its already open & there is no dialling between the 2 systems.
Any suggestions or idea's would be largely appreciated.

Cheers,

Greg Maiorana.