I've added a PAUSE of 1/10sec between the front trigger and the side trigger. This noticeably slows down the flashing of the LEDs on the SRF05s. In the audible range I can easily hear echos in a room. I have no experience with ultra-sound in the range that the SRF05 emits. The spec shows a time line in which the pulses seem to be a square wave of 2usec cycles. That is a little burst of 500,000 cycles per second sound that appears to last about 20 usec.

This little project keeps gets interestinger and interestinger!

If there were five cars racing near each other on this gymnasium track, would their SRF05's get confused. I don't think so, but I am not sure....

Ken