a pulsed sonar - based wireless rod position indication system that utilizes nuclear radiation and high temperature tolerant hardware . the pulsed sonar - based rod position indication system can precisely locate the rod position by measuring the time of flight of a transmitted signal and by using the phase and amplitude information of the same transmitted signal . primary and secondary antenna probes located in the interior of the control rod drive rod travel housing and full hardware redundancy provide for improved accuracy . the time of flight , phase and amplitude raw signals are inputted to a wireless data transmitter capable of sending the raw signals to a receiver antenna located elsewhere inside a containment for further processing .