Abstract: A two-stage cascade refrigeration system is provided having a first refrigeration stage and a second refrigeration stage. The first refrigeration stage defines a first fluid circuit for circulating a first refrigerant, and has a first compressor, a condenser, and a first expansion device that is in fluid communication with the first fluid circuit. The second refrigeration stage defines a second fluid circuit for circulating a second refrigerant, with the second refrigeration stage having a second compressor, a second expansion device, and an evaporator that is in fluid communication with the second fluid circuit. A heat exchanger is in fluid communication with the first and second fluid circuits to exchange heat between the first and second refrigerants. At least one of the first or second compressors is a variable speed compressor.

Abstract: A two-stage cascade refrigeration system is provided having a first refrigeration stage and a second refrigeration stage. The first refrigeration stage defines a first fluid circuit for circulating a first refrigerant, and has a first compressor, a condenser, and a first expansion device that is in fluid communication with the first fluid circuit. The second refrigeration stage defines a second fluid circuit for circulating a second refrigerant, with the second refrigeration stage having a second compressor, a second expansion device, and an evaporator that is in fluid communication with the second fluid circuit. A heat exchanger is in fluid communication with the first and second fluid circuits to exchange heat between the first and second refrigerants. At least one of the first or second compressors is a variable speed compressor.

Abstract: A two-stage cascade refrigeration system is provided having a first refrigeration stage and a second refrigeration stage. The first refrigeration stage defines a first fluid circuit for circulating a first refrigerant, and has a first compressor, a condenser, and a first expansion device that is in fluid communication with the first fluid circuit. The second refrigeration stage defines a second fluid circuit for circulating a second refrigerant, with the second refrigeration stage having a second compressor, a second expansion device, and an evaporator that is in fluid communication with the second fluid circuit. A heat exchanger is in fluid communication with the first and second fluid circuits to exchange heat between the first and second refrigerants. At least one of the first or second compressors is a variable speed compressor.

Abstract: A two-stage cascade refrigeration system is provided having a first refrigeration stage and a second refrigeration stage. The first refrigeration stage defines a first fluid circuit for circulating a first refrigerant, and has a first compressor, a condenser, and a first expansion device that is in fluid communication with the first fluid circuit. The second refrigeration stage defines a second fluid circuit for circulating a second refrigerant, with the second refrigeration stage having a second compressor, a second expansion device, and an evaporator that is in fluid communication with the second fluid circuit. A heat exchanger is in fluid communication with the first and second fluid circuits to exchange heat between the first and second refrigerants. At least one of the first or second compressors is a variable speed compressor.

Abstract: A compressor is controlled by generating and storing a compressor operation log. In addition, a compressor operation is selected from the compressor operation log in response to a sensor failure. Furthermore, the compressor is modulated according to the selected compressor operation in response to the sensor failure.

Abstract: To remotely diagnose and control equipment, a sensor attached the equipment is queried. This sensor generates a signal in response to an environmental condition of the equipment. In addition, the signal is received and a value is calculated based on the signal and a response curve of the sensor. Furthermore, the calculated value is compared to a range between a first value and a second value and a backup system attached to the equipment is modulated in response to the calculated value being outside the first value and the second value.

Abstract: An improved load-supporting system for scaffolding, lengths of elongated stock used in the construction industry, tools, and other loads includes a unique system for adjusting the height at which a load is held above a supporting surface. The invention includes a column having a column axis of alignment and at least one sleeve disposed about the column in coaxial sliding engagement therewith. The sleeve has an appendage forming a radially inwardly facing jaw and a jamming washer that surrounds the column and extends into the jaw. The height at which a load is held above a supporting surface is varied by adjusting the relative longitudinal positions of the sleeve and the column. By momentarily forcing the jamming washer into perpendicular alignment relative to the column, incremental adjustment of the relative positions of the sleeve and the column occur.

Abstract: A telephone test system (2) includes a controller (4), a programmable gate array (PGA) (24) and a digital signal processor (DSP) (26) connected by a common bus (20). The PGA (24) includes an output connected to an input of a digital-to-analog converter (DAC) (36) and input connected to an output of an analog-to-digital converter (ADC) (32). A driver circuit (46) is connected between the DAC (36) and a telephone circuit (60) and between the ADC (32) and the telephone circuit (60). Under the control of the DSP (26), the driver circuit (46) generates voltages to the telephone circuit (60) and samples the response of the telephone circuit (60) to such generated voltages. The driver circuit (46) includes control inputs for receiving from the PGA (24) an impedance adjust signal (D) and a resistance adjust signal (R). An output impedance (124) of the driver circuit (46) connected to the telephone circuit (60) is adjustable as a function of the impedance adjust signal (D) and/or the resistance adjust signal (R).