onevent prox
# if a sensor measures a value less than 300, it does not see the table
if[0]<300 or[1]<300 then 
    # stop the motors 
    # switch on a red light on the robot to signal an emergency stop 
    call, 0, 0)
    # if we do not see the edge of the table, switch off the red light
    call, 0, 0)