Been wondering if its necessary at all, to use any type of protector, ahead of a phone system using anything other than POTS lines.
Does COAX fed dial tone require protection?

Does the modem or digital equipment have its own protection.

No. If lightning makes it through an EMTA that the cable company provides or even over a Telco T1, there's nothing that you can do to stop it. Only true (and I mean real) copper POTS lines pose any kind of threat.

Thank you, Ed.