1. Check for the specifications which are recommanded for 
(like phone's size and color, no. of buttons and its size).
2. Check for the buttons working status.
3. Check for the logo printed on phone
4. once connection is given dial tone should be there
5. Telephone internal connection must be fine
6. Telephone must be Checked(Mark of Tested)
7. Telephone should have facility to Increase or decrease 
of ring volume
8. we should recieve msgs from other end once the 
connection is given

I think some kind of lazy interviewers throw this knid of 
non-sense questions. It is very clear to everybody that We 
do not go for testing until we are clear with each and 
every piece of functionlity. In this scenario they throw 
open-end questions like this and want to see the fun that 
is going to happen. Questions like these put the tester to 
more pressure. They force us to assume something about the 
shit and expect some kind of miracles in terms of 
testcases. So drill him on telephone with question.

Thanks
Jagadeesh

You are 100% Correct Jagadeesh!!!
But Testers are being faced these type of quite often.
How to face them

The best way is, that if there is any telephone on the 
interviewer table, just pick it up and throw it on his face.