The conventional way of interfacing with a lift is by using Inputs and Outputs.
An individual output on the access control controller will represent each floor.
The people that service the lift should be able to provide you a cable pair to represent each floor.
This cable pair will be wired into the output on the controller.
You will also need a cable in the travel cable for the proximity reader in the cab from the access panel (our new readers use 7 cores, max length 100 meters) the lift installation company should be able to provide this.
Once you start restricting many floors to different card privileges (known as destination control) you may need lots of outputs, we can add up to 64 outputs per controller using extension boards.