Two lines for one extension

Hi to all,

in our organization many users have two lines, one desktop (main) and one mobile (secondary); each one has different extension number, main is e.g. 65, secondary is 1065.

The strategy should be that main extension ring, after timeout secondary extension is rung. When one of two is busy, either for incoming call or outbound generated call, a new incoming call should be returned as busy.

Now, I get successfully working such ring strategy with the follow-me, but on the busy issue I didn’t find yet any solution (I also tested with a queue), when secondary extension is busy then main can still receive incoming calls.

Thank you in advance.