we use CallManager to support emergency evacuation in a dam. Currently it's done by dialing an extension hooked to VG224 with an altered ringtone, which then goes to a Viking VG-10 to amplify the signal and run remote analog bells in the complex.

The potential flaw in the system is that it requires the initiating phone to stay off-hook, meaning the person at that localtion can't call for help, etc.

I'd like to engineer a solution that would initiate the call and then auto-transfer the call off the originating phone. My initial thought would be to auto-transfer the call to a Call Park and leave it there. The solution must work from both IP and analog phones. any ideas?