A simple question about the ultrasonic range sensor

[NoEinstein]

There are two "eyes" on the ultrasonic sensor and I'm just wondering if one is an emitter and the other is a receiver or if they both emit a pulse and then both detect the pulse as it returns. It's a simple question, but I haven't found anything answering this question in any of the documentation anywhere. Thanks.

 

[JimPerry]

One sends the other listens in most ultrasonic circuits

 

[g6ejd]

I checked the circuit diagrams and one transmits and one receives, but there is no reason why a single unit could not do that, like car sensors. I suspect it's a compromise between range, accuracy and timing that drives the need for two.

 

[NoEinstein]

Thanks, guys! The mystery is solved!