If you have the call waiting service on your phone line, when you are connected to the internet and a call comes in you may be disconnected from the internet.

Solution:

1. The tones from incoming calls when Call Waiting is enabled on your phone service can cause your modem to disconnect. To prevent this you can disable Call Waiting on a call-by-call basis by prefixing the telephone number with *44. For example to call Integrity Network Solutions access number you would dial *44 1832,43849900. At the end of the call Call Waiting will resume without you having to re-enable it.
2. Alternatively you can turn it off by dialling: #43# on your phone pad. Don’t forget to turn it back on (*43#) when your done if you want to activate call waiting.
3. Selecting the Call Waiting option built into Windows won't function as it was intended for the US telephone system. You should leave this option turned off.

The examples above assume that your phone connection is with Telstra. These codes may be different for other providers. Please check with your provider.