In all sensitivity settings (except maximum), the line must travel the specified distance in the same direction and within 2 seconds in order to trigger the unit. Any movement in the opposite direction will reset the distance counter to zero. This can substantially reduce, or eliminate false triggering caused by wind and water movement. Battery life indication when receiver is switched on (4 x green LEDs indicates full/close to full, 3 x green LEDs indicates the batteries are used, but do not need replacing, 2 x orange LEDs indicates the batteries are becoming low, 1 x red LED indicates batteries are low and need replacing) You can pay with Paypal or Credit Card. Small items are sent with Royal Mail and larger parcels with my Courier. Courier postage costs are mainland UK only (Exc Highlan