Efficient Dog Fencing System: The transmitter,receiver and boundary wire forms an effective fencing system together to deter our dogs from the designated area,which greatly ensures our pets' safety. The boundary wire creates an effective signal field when the transmitter is working. If your dog tends to walk out of the boundary,the transmitter will emit a harmless radio signal. Once the signal is detected by the receiver,it will automatically start warning beep,vibration or static shock to urge your dog to go back into the boundary. 3 Effective Correction Modes: The receiver works automatically once you start up the system. If your dog walks out of the boundary,the preset correction signals will be delivered cycle by cycle until the receiver battery is out of power. Mode 1:Beep+Vibration;Mode 2: Beep+Low Level Shock;Mode 3:Beep+High Level Shock. We also offer 20 training flags for you carry out proper training to ensure that the dog understands the boundaries and responds appropriately to the correction signals. Adjustable Signal Width & Multiple Dogs Support: One transmitter can pair with multiple receivers. The transmitter also comes with 1.77 acre signal field range and 9 adjustable levels. The signal width can be increased .5m/1.6ft per level from boundary wire to warning zone and from boundary wire to static correction zone. The wire break warning can tell you in time if the wire is broken. The 'OK' indicator tells if the loop is right.