LSL Wiki : llSensorRemove

llSensorRemove();

Removes the sensor set by llSensorRepeat.

Note that unlike a listener, there is no need to specify the sensor by key. This is because objects can only contain one sensor per prim.

Note: llSensorRemove() clears out all data of the detection functions. So, always gather all data you need before calling this function.

Here's an example written by Aniam Ingmann explaining llSensorRemove():
Example:

default
        {
        on_rez(integer sp)
        {
                  llResetScript();//Always make sure the owner is updated.
        }
        state_entry()
        {
                  llListen(0,"",llGetOwner(),"");
        }
        listen(integer c, string n, key id, string msg)
        {
                  if (msg == "sensor on")
                             {
                                      llSensorRepeat("",NULL_KEY,AGENT,96,PI*2,.1);//Turns on the sensor to look for agents within 96m
                             }
                  if (msg == "sensor off")
                             {
                                      llSensorRemove();//Turns off the sensor.
                             }
                  }
         sensor(integer n)
                  {
                             //whatever you want to pop up when someone is detected in the sensor.
                  }
        }

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Functions / Sensor Functions