Pet owners have long struggled with adequate measures of pet containment. Inadequately confined pets run the risk of damaging property and endangering the animal. Physical barriers such as fences can be quite expensive and often not aesthetically pleasing. For over 20 years a number of pet containment systems have been developed to keep animals to predefined areas. Imbedding a wire perimeter and connecting to a transmitter system has been a popular method. The pet wears a collar that has a receiver and a motivation system for providing a stimulus to the pet as it approaches a boundary. Limitations have been the cost associated with the wiring and the fact that the pets are unable to re-enter the boundary area if they escape. There is also the problem that a lawnmower can damage wires not buried properly. To overcome this limitation, wireless systems have also been developed. The receiver only produces a stimulus when there is a loss of signal from the pet.
In radio collars there is a safe area in which the pet can roam without receiving a warning stimulus. When the pet moves away from this area the collar/receiver gives a warning signal (a shock, loud sound, or other stimulation) to the pet. Therefore the pet learns to stay within the safe area. The collar unit comprises a multiplicity of radio signal receivers each having a receiving antenna. The system transmitter continuously transmits a radio frequency (RF) signal and a mobile receiver assembly mounted in the collar unit on the dog. The receiver assembly receives the RF signal and measures the intensity of the received signal.
Early patents for underground pet containment systems were granted in the early 1970s. Documentation as to who the original inventor was is not available but technology from electronic transmission had been in use for Global Positioning System (GPS) since the early 1960s to track animals in the wild. The desire to keep pets safe and away from restricted areas in private homes (such as gardens and children's play areas) moved the technology into the home market.
The materials for the collar range from nylon to leather with a metal buckle and D-ring to hold the collar in place. Suitable wiring and electronic components consist of oscillators, transistors, capacitors, and resistors that are incorporated in the receiver and transmitter devices. Systems using buried wire containment systems use heavy duty 18-gauge wire.
Some radio collars use a wire imbedded in the ground to transmit signals to the receiver. Other forms use only a transmitter box and the collar, avoiding the wire. Depending on the device's strength, it can cover anywhere from 50 to 500 yd (46-457 m). The level of intensity will also vary depending on the size and temperament of the dog. There are separate devices for smaller, larger, or more stubborn dogs.
1 A dog collar can be made out of many materials, though nylon is the
- 2 The edges of the collar are heat sealed to prevent loose threads.
- 3 The material is then taken to a press that punches round metal rivets through the collar, simultaneously removing the material in-between the rivets. The rivets enable the buckle to hold the collar together.
- 4 Next, the collar is attached to a preformed metal buckle. The buckle generally arrives at the plant already formed. The fabric of the collar is fed through the bottom of the buckle and a D-ring. It is then folded back onto itself and manually stitched using an industrial sewing machine, securing the buckle in place. The collar is now ready for the attachment of the RF receiver.
- 5 The RF receiver arrives at the plant preformed. It is put on an assembly line and then manually placed in plastic cases. The cases have been made by heating plastic pellets and injecting them into a liquid mold.
- 6 A 6-volt battery is attached to the radio receiver. The RF receiver is mounted on the lower portion of the collar along the strap by mechanical fasteners (screws, bolts, rivets, etc.) that pass through the strap and clamp the plate from the housing of the transmitter.
- 7 The parts of the transmitter also arrive at the plant preformed. The transmitter consists of a printed circuit board that is connected to a correlation point of the capacitors and to the ground through a resistor. The resonator circuit may be a Liquid Crystal resonator circuit or a circuit including an electromechanical converter element (an element that converts electrical energy to technical energy), such as a Surface Acoustic Wave Resonator (SAW), a crystal resonator, a lithium-tantalite resonator, or a tantalite-niobate resonator.
- 8 In this transmitter, an oscillation loop is formed by a closed circuit including the resonator circuit, the antenna, and the base and emitter of the transistor, which constitutes the oscillator.
- 9 The collector of a transistor is connected to the ground through a series of circuits including bias resistors as well as to the power voltage.
- 10 The base of the transistor is connected to the ground through a series circuit including capacitors. The base is also connected to the ground through the connecting point where the resistors are connected, and where a series circuit of an antenna and a resonator circuit is also connected.
- 11 A flexible antenna consists of two copper wires wrapped in a form of plastic installation. It typically extends out of the transmitter and is directed upward by a guide attached to the side of the device.
- 12 The bottom of the antenna includes a through-hole through which a threaded stud is attached to the transmitter, used to couple the antenna to the transmitter and broadcast signals to the receiver.
- 13 The transmitter is then placed in an injection molded plastic case, manufactured in the same manner as the receiver case on the collar.
- 14 The wire used to mark the borders of the electric fence is a roll of 18 gauge multi-stranded wire. The wire is insulated within a plastic coating and arrives at the plant in large rolls. The wire is then automatically cut into 500 ft (152.4 m) rolls.
- 15 Once the transmitter is finished, it is w packaged with the wire rolls and collar. The packages are then shipped to either the distributor or directly to the customer.
Skilled technicians at work stations perform calibration tests such as soldering inspection, high and low voltage vibration, and humidity thermal cycling. The receivers are tested to ensure that the correct amount of voltage or level of sound is distributed when activated. The collar is also subjected to tests such as strength and durability.
Waste materials (discarded wire and electrical components) are disposed through industry waste removal. Any plastic that can be reused is melted down and remolded. When the collar material is defective, it is discarded.
Future systems are being designed that use orthogonally positioned antennas to ensure boundary signals are detected. The risk of inadvertent shocks from nonboundary RF signals has been greatly reduced by encoding the transmitter with a preselected signal eliminating errant shocks from abhorrent RF signals. Additionally trapped animals will no longer continue to receive corrections until the battery is drained of power. The shocks are suspended but the circuitry continues to monitor for the boundary signal. Microprocessor circuitry is used to analyze the received signals and to control the annoyance signals. The microprocessor circuitry is also be powered down when not in use and then turned back on when a signal is received to be analyzed to further conserve power. Additionally, the circuitry may include one or more motion sensors that allow the power-draining circuitry to be energized in response to movement of the animal such that when the animal is at rest and not trying to cross the boundary, the battery is not wasted trying to detect a boundary signal that should not be present.
Where to Learn More
Radio Fence Distributors, Inc. Web Page. December 2001. < http://radiofence.com >.
United States Patent and Trademark Office Web Page. December 2001. < http://www.uspto.gov/patft/index.html >.
Woolf, Norma Bennett. "Hidden Fences, Out of Sight May not Mean Peace of Mind." Dog Owner's Guide December 2001. < http://www.canismajor.com/dog/fencesl.html >.
Bonny P. McClain