Complex sentence: Asterisk supports most SIP telephones, acting both as registrar and back-to-back user agent, and can serve as a gateway between IP phones and the public switched telephone network (PSTN) via T-or E-carrier interfaces or analog FXO cards.
Split into simpler sentences: Asterisk supports most SIP telephones, acting both as registrar and back-to-back user agent. It can serve as a gateway between IP phones and the public switched telephone network (PSTN) via T-or E-carrier interfaces or analog FXO cards.