EAS/CAP Equipment Rundown


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So now that we know something about IPAWS, let's take a look at CAP itself. A document from the OASIS website has all the fine details.

As the end-user of new CAP-ready equipment this is likely way more than you'll want (or need) to know. What you can glean from that paper is this:

  • CAP is a simple but general format for exchanging all-hazard emergency alerts and public warnings over all kinds of networks
  • It encompasses geographic targeting using latitude and longitude shapes and other geospatial representations in three dimensions
  • It allows for multilingual and multi-audience messaging
  • It allows for phased and delayed effective times and expirations
  • It allows for updates and cancellations
  • It makes use of templates for the creation of warning messages
  • Compatible with digital signature capability
  • Has facilities for audio and images

    There again, as an end-user you won't necessarily be concerned of the nitty-gritty details on how it works; just that it will work with the gear you procure and with the way you plan to install it. It is clear that the intended method for the distribution of the CAP messages is via the public internet. Part of the FEMA initiative with IPAWS is to develop a system known as IPAWS OPEN (Open Platform for Emergency Networks) that can accept emergency messages of different types (such as EAS) and then distribute them outbound to the appropriate dissemination points (such as radio and TV stations and cable systems). What isn't clear is whether the messages will be retrieved by the local CAP unit (pull) or whether a server (such as IPAWS OPEN) will send messages to your CAP unit (push). Each method has its advantages and disadvantages. If your unit pulls CAP messages (by poling a server on a regular basis) the advantage is that you will make use of the normal security measures already in place when any LAN is set up to access the internet -- in other words, an internet-facing router is in place performing firewall functions. Obviously you would want to specify the poling frequency as being fairly frequent so that your system can respond to a real emergency in a timely fashion.

    If messages are pushed to your CAP decoder, then one of two methods can be used for network security. If the CAP decoder lives on your LAN, then your internet-facing router must be configured to expect to see incoming messages addressed to a certain IP address (that of the CAP decoder) using a specific destination port number. If this isn't done then the firewall would ignore the CAP messages that hit it from outside via its public IP address. Another approach would be to use a device that has two Ethernet ports; one port would be on your LAN, the other port on a separate internet connection (like a DSL or cable modem) that is either open to the internet (probably not a good idea) or connected to the internet via a separate, perhaps less complex firewall.

    In either case it'll be important to have the CAP device generate log entries that will include whether or not it is receiving the expected 'pushed' messages (which should include some sort of 'keep alive' messages) or whether or not it is able to reach the server from which it 'pulls' messages. Part of the station's EAS routine will then be sure that these routine messages are indeed going back and forth, so that the system is known to be ready in the event a real message comes down.

    One thing that appears clear with respect to CAP implementation (and there aren't many at this point in time) is that you will not necessarily need to replace your current EAS system completely. It will be possible to add what amounts to an external CAP decoder that then becomes an additional source of EAS messages for your legacy system. The other option of course is to use the new legal requirements as a reason to upgrade your EAS equipment to the very latest, CAP-integrated versions.

    Whether the CAP requirement becomes law next March, or sometime later, one thing is for sure: it is coming, and soon. This is obviously a good time to make plans for compliance, and to budget accordingly in next year's capital budget. While the exact details of how this will all work are still being worked out, enough is known so that adequate amounts of capex can be set-aside for the new equipment.


    For a comparative rundown of available EAS/CAP equipment, follow the link below.


    EAS CAP Equipment Rundown Table

    Want to know what equipment is available to make your station CAP compliant? Here's a list.

    Irwin is transmission systems supervisor for Clear Channel NYC and chief engineer of WKTU, New York. Contact him at doug@dougirwin.net.




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