field service crew unsure of their location can scan to see which wells are close by and then look at oilfield map to determine their approximate location examples of the signals exchanged between the handheld controller hh and the well are as follows when a crew presses u201c scan u201d the controller transmits a 6 second continuous tone this will incidentally block transmissions from any other handheld controllers in the vicinity which may help alert the service crews that another crew is working nearby 1 hh scan 6 second continuous transmission to wake up receivers u201c u201d this does not include any unique identifier associated with any particular well or rather a wireless interface associated with a specific well therefore none of the wireless interfaces of any wells will filter out the signal and all will respond to avoid collisions the wireless interfaces are programmed to respond after a short random delay 2 wells random time after tone end u201c to hh scan hello from xxx u201d where xxx is replaced by the id number or code of the well in question the handheld controller then builds up a list of the wells within range from the received hello messages the user can then pick a specific well and ask for the well parameters to be displayed where xyz is the pre programmed code for a specific parameter or group of parameters all wells other than well xxx will then filter out or otherwise ignore this message but well xxx will respond with the requested data the user can thus confirm that they are in the vicinity of the correct well and that it.