Since I mentioned in a previous topic that there's free ALE decoding software available, here's the URL for it:
ALE is basically used for digital signalling, path testing and comms establishment by military, diplo and many commercial interests. Sometimes an ALE call will be followed by a transmission (it may not be on the same frequency) in another mode; sometimes voice, sometimes not.
It takes a bit of practice to read the headers and get the IDs correctly; your best sources for this is Utility Monitoring Central, Mike Chace-Ortiz's site (which has numerous links to other software, ALE ids and much more) at:
and the Worldwide Utility News listserver at qth.net, which has been mentioned here numerous times.