
CAP stands for Common Alerting Protocol. CAP is a new internationally-accepted open standard for sending information about emergencies. In the US, CAP is going to be implemented as part of the IPAWS (Integrated Public Alert Warning System) program. FEMA will originate messages about emergencies and send them to a centralized "aggregator", which will then disseminate the messages over the internet.
Unlike the current EAS system, where messages only go out over TV and radio, CAP is not tailored for broadcasters. CAP messages may include text, photos, videos, or audio to supplement the basic information. The messages will be sent not only to TV and radio stations, but also to computers, smart phones, highway signs, and more.
The FCC will require you to have equipment that can receive and decode CAP messages. You will also need to be capable of rebroadcasting CAP messages in EAS format.
The current deadline for compliance is June 30, 2012. The original deadline was March 30th, 2011, but the FCC has extended it twice at the request of Prometheus and other broadcasters' associations.
You can find more information in the following link
http://prometheusradio.org/eas_cap_basics