1. Technical Field of the Invention
The present invention relates to an electronic fence, and more particularly, to an electronic fence capable of guiding animals under training to return to a predetermined restricted area.
2. Description of the Related Art
FIG. 1 shows a conventional electronic fence. In FIG. 1, transmitter 100 is connected to a transmission wire antenna 110 for transmitting an electric wave. Transmitter 100 includes an electric shock level control 101 for setting the level of an electric shock to be applied to animals, an antenna checking lamp 102, a power switch 103, and a transmitter power level control 104.
The operation of the conventional electronic fence will now be explained. A user turns on the power switch 103 included in the transmitter 100 and operates the shock level control 101 of the transmitter 100 to set the level of the electric shock to be applied to the animals. In addition, the user operates the transmitter power level control 104 to set a predetermined transmitter power level. Then, the transmission wire antenna 110, included in the electronic fence to prevent the animals from escaping, is operated to generate a signal.
In this state, when an animal wearing a receiver approaches the fence, a receiving antenna receives the signal transmitted from the transmitter 100 and a detector demodulates the received signal into the original signal. When the demodulated signal is an electric shock, the receiver generates a electric shock, having the level corresponding to the level of the transmitted signal, through a pair of electrodes. Accordingly, the animal cannot get out of the transmission wire antenna 110.
However, the aforementioned electronic fence generates an electric shock having a constant level when the animal escapes from a restricted area, and thus it is not efficient. Furthermore, the electric shock is generated when the escaped animal returns to the restricted area. Thus, the animal cannot enter the electronic fence due to the electric shock and the animal may run away.
When excited, some animals can run at speeds up to 100 Km/hour (62 miles/hour). At these speeds, the animal can escape the restricted area before an electric shock is applied to them. Furthermore, when the animals calm down and return home they typically return at a much slower pace. The conventional electronic fence cannot detect the direction the animals are moving relative to the restricted area and will generated the electronic shock as the animals attempt to enter the restricted area. If an electric shock is given to the animals when they are returning to the restricted area, the animals are deterred from entering the conventional electronic fence and may run away and become lost or injured in car accidents.