My internet connection disappears when i hang out the phone.?

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I have an ADSL connection. I use a splitter to connect my phone and Modem to the telephone lines. whenever I hang out the phone, the internet connection disappears.....when i pick it up...tadaaa.....can someone tell me the reason..I think its the telephone lines somewhere touching.....sometimes it disappears when I pick up the phone....and sometimes its normal.....