3CX does not support any hardware inside the box. All communications is done with SIP devices. There are tons of SIP devices to handle single phone lines to those that can handle T-1's.
PBX's like Asterisk do what your talking about, but 3CX decided to take a different approach and not worry about having to support a ton of different cards which is pretty smart as they can concentrate on the PBX software itself and not on drivers.