Wifi doesn't work

Dear all,

I've got a problem with my wifi router, 
here are the situations and need advice for troubleshooting.

・Its model is DG834G

・Internet provider is talktalk and the router also connect to home phone

・I was using wifi without any problem last night on my computer,

    but once my landlady start phonecall at the same time, 

   a sound like an alarm came up and the connection went into trouble

・After the phone call, I can still see wifi connection on my computer,
but I cannot access the internet.
・When I check router, only power mark and a mark like a signal show light,

but the other signals which usually light does not show anything.

How can I solve this?