When you use Phone Dialer make a voice call, video call, or conference video call, in Windows XP SP2, the call is immediately disconnected after you dial.

This behavior will occur if a firewall, on either computer, blocks port 1720.

To open port 1720 in the Windows Firewall:

> 01. Start / Run / wscui.cpl / OK.

02. Press Windows Firewall at the bottom of the window.

03. Clear the Don't allow exceptions box on the General tab.

04. Select the Exceptions tab.

05. Press Add Port.

06. Type Phone Dialer (1720) into the Name box.

07. Type 1720 into the Port number box.

08. Check TCP.

09. Press OK 10. Check the Display a notification when Windows Firewall blocks a program box.

11. Press OK until the dialog closes.

To place a Phone Dialer call:

01. Start / Run / dialer.exe / OK.

02. On the Phone menu, press Dial.

03. Type, or select, the computer name or IP address in the Connect to box.

04. Press Internet Call.

05. Press Pace Call.

06. Click Unblock and OK to the TAPI 3.0 Dialer and IP Multicast Conference Viewer security alerts.