The Enhanced 911 (E911) system is a separate telephone system from the regular PSTN system. So CAMA is a protocol used to ensure that a call from a particular number is routed to the Public Service Access Point (PSAP) which is designated to handle calls from that number. The PSAP is alse responsible for dispatching emergency services.
CAMA has the capability to send both calling and called party in-band and the calling party is used for call routing in the E911 telephone system.
