No no no no.
Just dial 911 then once they reply via the tdd. Just inform that it is for test to dial the 911 via the TDD. Be sure to thank shortly since 911 always records your converation. Just be nice and I do not want to see you getting into trouble with police officers. 
Do not hestiate to contact. Just dial 911 to ensure that your landline without service still works.
I have tested 911 in a big city. The 911 operator understood and gladly to assisted me.
Let me know if your phone without service still works for 911.
Thanks
