A Ping ultrasonic ranging module can measure distance based on the time it takes for sound to travel to an object and for the echo to return to the module. The user must provide a positive logic pulse to generate the burst of ultrasound (bang). Immediately after the bang, the module output goes HIGH until the echo is detected and it goes back LOW. The time HIGH for the output pulse is proportional to the distance from the object that caused the echo. However, the Ping module has only a single pin that serves as both input and output. Use tristate buffers and any logic gates necessary to allow a single active- HIGH push button input to pulse the signal pin and immediately after this pulse is finished to allow the signal pin to drive an output.