Modem Disconnection

I just recently installed a Motorola SM56 Voice Modem to my Acer Computer. After installing the driver i tried my dial-up but after a couple of click the modem disconnect right away. I tried it again but this time i listened to the receiver. I heard the modem dialed the number, but disconnect after a couple of seconds, however when i listen to the phone it was able to dial my ISP and connect but then the modem was disconnected already.

What did i do wrong…how do i resolve this kind of problem?