Hi,
What exactly are you trying to do?
What is the application?
Is it a doorbell type project.
You would be better to put the controller and ultrasonic at the ground floor, and push a tone on the power leads back to the upper floor, with another controller to detect the tone and activate your alarm/LED or what ever.
A tone will not be as time sensitive as your ultrasonic control pulses.
In fact using different tones you could transmit different situations.
Just a thought.. Tom... 
