HiLetgo One Pair 16MM Ultrasonic Sensor Probe Split Ultrasonic Transceiver+Receiver

Nice transducer. Works as specified. I use them in robotics, and The last application was proximity sensing to a Magic Book for Halloween. The closer someone got to the book, the brighter the pentagram on the book's cover would light. The price is very nice for this sensor.

I used one of these for the build of a directional ultrasonic detector to help find electrical arcs... The pickup seems to be exactly 40KHz as advertised, and my mixer ( mixed with 39Khz oscillator) circuit worked well, down-converting that to an audible 1Khz signal that can be heard in my headphones. I ran these across my component analyzer and saw no difference between the ones marked "R" (receiver) and "T" (transmitter), nor noted any physical difference, so they may in fact be "the same", but I did NOT evaluate receive gain to a fixed input, etc. - I just went ahead and made sure I used one marked "R" for "receiver". They both read as a "capacitive component" of (2200 picofarad), and require no bias voltage like a condenser (audio frequency range) microphone.

Worked well used them as sensors on raspberry pie.

Units work as described. I do not se any difference between Rx and Tx in addition to the T and R marking. They both seem to perform the same as transmitters or receivers. The big ring on the transmitter pin does not mark polarity. If you are going to use transmitters in parallel you must measure the output and reverse the wiring if phases are reversed. You need an oscilloscope to test this. 4* because of the random marking. Otherwise, no issues.

Nice little 40KHz transducers. And 40KHz they are! Testing showed that they resonate precisely at 40KHz (i.e. their output power "volume" drops off sharply above and below 40KHz). Got no complaints - they do what they are designed to do - at exactly 40KHz.