There are two methods to connect.

Option (1) Layer 2 Tunneling Protocol (L2TP)

You need a Cisco router (e.g. 2811) and PoE switch (e.g 3560) and 6 phones (3 x 9971 with camera and 3 x 7965).

Option (2) Software control of phones in rack

You can control the phones that are directly connected to the rack. All you need at your end is the Cisco VPN Client and you can be up and running in seconds.