Question : Telnet with public IP will not connect

I have a Samsung iDCS phone system with Voice Mail that I can access via Telnet using the network port and the private IP I assigned it. I used a 1-to-1 NAT on my firewall and assigned it a public IP. Using this IP it will not connect.
I tested the Telnet service through the firewall using another server with the same setup and was successful.
Why can I not connect to my phone system this way?

Answer : Telnet with public IP will not connect

As far as I can tell the system has no way to add a default route to it. It has the capability to add a remote VOIP network, which is essentially adding a static route, but it does not seem to have the capability to add a default route. So, most likely, your telnet connection reaches the device, but the device does not know how to get back because it does not have a default route. This seems to be a deliberate security limitation.