"Single unit only required, a short pulse of 0.5ms 40kHz is applied to the unit, the unit then acts as a receiver to detect the presence or distance of an object. "
You need to do 2 things:1. Generate a 40KHz square wave burst to feed to the transducer. You can do this by programming one of the three counter/timers in the Arduino. I suggest you use counter/timer 2.2. Detect the received 40KHz pulse. The ADC in the Arduino is too slow to do this, so I suggest an op-amp followed by capacitor/diode/resistor network to generate DC, which you can then read via an Arduino analog input. This circuit has to be able to withstand the transmitted signal appearing at it input, and then recover quickly enough to respond to the received signal. Use an op amp that can run from a single 5v rail, to avoid the possibility of overdriving the analog input.
oh boy, i guess its way harder than i was expecting. Specially having no knowledge about frequencys and currently have no Oscilloscope.They sell them without a pair, and specify that "Single unit only required", so im guessing this sensor has the receiver and transmitter inside.