Abstract: A method of operation of a pet door system with a controllable lock and circuitry including a resonant circuit having an antenna and an element to vary the resonant frequency of the circuit according to a setting parameter, a drive circuit for driving the resonant circuit with a drive signal, and a demodulator, the method including a setting-up operation comprising varying the setting parameter while driving the resonant circuit at a first driving frequency, detecting a first value of the setting parameter at which the resonant circuit is substantially in tune while the resonant circuit is driven at the first driving frequency, and storing the first value of the setting parameter. The method further includes a reading operation comprising reading the first value, driving the resonant circuit at the first driving frequency with the setting parameter set to the first value, and attempting to derive data from the demodulator.

Abstract: A system of locating a moveable RFID transceiver, in which the moveable transceiver is capable of sending and receiving TOF (Time of fight) signals, and also includes battery powered base stations suitable for outdoor use, and capable of sending and receiving TOF signals. The system measures the signals to derive time of flight information between the moveable transceiver and the base stations and using this data to calculate the position of the moveable transceiver. The position of the base stations may be fixed using TOF signals before attempting location of the moveable RFID transceiver. The base stations may be solar powered, and can work with a base network of only 2 base stations.

Abstract: A method of operation of a pet door system with a controllable lock and circuitry including a resonant circuit having an antenna and an element to vary the resonant frequency of the circuit according to a setting parameter, a drive circuit for driving the resonant circuit with a drive signal, and a demodulator, the method including a setting-up operation comprising varying the setting parameter while driving the resonant circuit at a first driving frequency, detecting a first value of the setting parameter at which the resonant circuit is substantially in tune while the resonant circuit is driven at the first driving frequency, and storing the first value of the setting parameter. The method further includes a reading operation comprising reading the first value, driving the resonant circuit at the first driving frequency with the setting parameter set to the first value, and attempting to derive data from the demodulator.

Abstract: A self-cleaning assembly comprising an enclosed casing 1 with a movable piston 31 and filters 32,33 therein. The preferred assembly has a casing 1 with a dirty water inlet 5, a first outlet 6 for clean filtered water and a second outlet 7 for the removal of sludge from the casing. The filter assembly is constructed and arranged to provide, in its normal operating mode, a liquid flow path through the filter 32,33 in a first direction between the dirty water inlet 5 and the clean water outlet 6 and, in a cleaning mode, to provide a liquid flow path in a second direction between the dirty water inlet 5 and the sludge outlet 7. In the cleaning mode, the movable member 31 compresses the filters 32,33 during the liquid flow in the second direction and contaminant is released therefrom for removal from the filter assembly via the second outlet 7. In an alternative embodiment, the sludge outlet 7 is omitted and sludge is removed from the casing via the outlet 6.

Abstract: A self-cleaning assembly comprising an enclosed casing 1 with a movable piston 31 and filters 32,33 therein. The preferred assembly has a casing 1 with a dirty water inlet 5, a first outlet 6 for clean filtered water and a second outlet 7 for the removal of sludge from the casing. The filter assembly is constructed and arranged to provide, in its normal operating mode, a liquid flow path through the filter 32,33 in a first direction between the dirty water inlet 5 and the clean water outlet 6 and, in a cleaning mode, to provide a liquid flow path in a second direction between the dirty water inlet 5 and the sludge outlet 7. In the cleaning mode, the movable member 31 compresses the filters 32,33 during the liquid flow in the second direction and contaminant is released therefrom for removal from the filter assembly via the second outlet 7. In an alternative embodiment, the sludge outlet 7 is omitted and sludge is removed from the casing via the outlet 6.

Abstract: A self-cleaning assembly has an enclosed casing with a movable member/piston and a filter therein, the casing having an inlet and a first outlet for liquid supplied thereto and a second outlet for removing liquid containing contaminant from the casing. The filter assembly is constructed and arranged to provide, in a normal operating mode, a liquid flow path through the filter in a first direction between the inlet and the outlet and, in a cleaning mode, to provide a liquid flow path in a second direction between the inlet and the second outlet. The movable member compresses the filter during the liquid flow in the second direction and contaminant is released therefrom for removal from the filter assembly via the second outlet.

Abstract: A pond pump having a housing (1) enclosing a synchronous motor (9) with a drive shaft (40) on which an impeller (20) is loosely fitted so that, on start up, the shaft (40) can rotate relative to the impeller (20) until a pair of diametrically opposed keyways (43) on the shaft engage and entrain keyways (27) on the impeller (20) to rotate it continuously in one direction. If the drive shaft initially rotates in the opposite direction, pegs (25) on the rear face of the impeller (20) engage with a detent (60) located behind the impeller (20) to stop said rotation until the motor (9) restarts and rotates the drive shaft (43) in said first direction. One end of the drive shaft (40) is received in a first bearing (50) mounted in the housing (1), the other end of said shaft being received in a blind bore (28) in the impeller (20) which is coaxial with the axis of rotation of the shaft (40).

Abstract: An electro-magnetically controlled pet door having a door (1) pivotally mounted in a door aperture (17) of a frame (2) and an electrically controlled catch mechanism normally preventing opening of the door in at least one direction that is released when a magnet (30) carried by an animal approaching the door is sensed by two or more reed switches (23,24) on or in the frame mounted and connected electrically in parallel. The switches (23,24) are disposed in an array extending circumferentially of said door aperture and have normally open contacts and magnetic biasing means (26,27) are associated with the reed switches and positioned laterally thereof to increase their sensitivity.

Abstract: An electro-magnetically controlled pet door having a door (1) pivotally mounted in a door aperture (17) of a frame (2) and an electrically controlled catch mechanism normally preventing opening of the door in at least one direction that is released when a magnet (30) carried by an animal approaching the door is sensed by two or more reed switches (23,24) on or in the frame mounted and connected electrically in parallel. The switches (23,24) are disposed in an array extending circumferentially of said door aperture and have normally open contacts and magnetic biasing means (26,27) are associated with the reed switches and positioned laterally thereof to increase their sensitivity.