Typically a DACT communicates with the FACP via relays, alarm, trouble, & supervisory. Unless the FACP & DACT have a compatible method of communication like an annunciator bus or RS-232.
This would depend on what model FACP & DACT you have. Most FACP models now have a DACT built-in or one that can be added inside the FACP cabinet.
In the older days the DACT would communicate to central station via 2 phone lines. Now NFPA 72 requires two separate methods of communication, 1 phone line, 1 IP, cellular, or radio dialer. Otherwise you could use a solepath dialer like the Telluar TG7 cellular dialer.