Prevent Phreaking

A challenge...

We are developing information kiosks that will have handset connected to the Line-in RJ 11 socket of an internal PCI modem. The handsets have no keypad and are intended for making restricted calls to emergency services and our own sites. The handsets currently have a ringtone when taking off-hook and if the right DTMF tones can be simulated I believe free calls are easily achieved. I am a software person and have a limited knowledge of Telcoms. However I thought it may be possible to disable the line-in port when not in use, maybe using AT commands, I found out the '&Jn' extended AT command disables the port but I have yet to find a modem to supports this. Does anyone know of modems I could test this on, any better method for providing the necessary security measures or any helpful pointers???

Best Regards


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