Abstract: A method includes cycling an electronic evaporator pressure regulator valve fluidly coupled to a refrigeration circuit to regulate flow through the electronic evaporator pressure regulator valve and sensing a current drawn by the electronic evaporator pressure regulator valve during cycling of the electronic evaporator pressure regulator valve. The method further includes determining a valve condition of the electronic evaporator pressure regulator valve based on the sensing.

Abstract: An apparatus for refrigeration system control includes a plurality of circuits, each circuit having at least one refrigeration case and an electronic evaporator pressure regulator in communication with each circuit. Each electronic evaporator pressure regulator controls a temperature of one of the circuits. A sensor in communication with each circuit measures a parameter from the circuit. A controller associated with each electronic evaporator pressure regulator controls the respective electronic evaporator pressure regulator based upon measured parameters from each of the circuits.

Abstract: A communications system has an active master node which transmits request messages in serial bit fashion on a data bus, and a plurality of responder nodes each of which receives the request messages on the data bus and may respond to a request message with a serial bit answer message. The possiblity exists that a plurality of responder nodes may provide concurrent answer messages forming a composite signal which the active master node may not be able to recognize as containing answer messages. A low pass filter is provided in the active master node which provides as its output only those pulses in the composite signal whose length is within a predetermined interval, typically from approximately a tenth to one half of the interval for each bit in the answer messages. A counter receives the low pass filter output and provides a collision signal to the associated master node if more than a preselected number of pulses within the predetermined interval are present.

Abstract: An electronic network of communication and processing nodes particularly suitable for control of environmental systems has pluralities of the nodes which are sources for certain types of status messages each of which comprise communication of a particular kind of information on the network. To resolve the question of which of the nodes shall furnish each type of status message, one node is designated the coordinator node, and it stores a status message source list which associates the node assigned for each type of status message with the status message type itself and transmits all or a part of the list on the network to allow each of the status message source nodes to determine therefrom their responsibility with respect to each status message type. These status message source nodes can also transmit request messages on the network by which they request responsibility for furnishing a particular type of status message.

Abstract: A communication network has one master node which maintains an active master list (AML) containing the node addresses of all nodes to which the token will be passed. When nodes are added or deleted from the network, it is efficient in terms of data bus occupancy and individual processing time by the nodes if the successor address for each node is broadcast in a single message, and the availability of an AML makes this possible. The network has the capability of efficiently updating the AML whenever the configuration of the network is so changed.

Abstract: A communication system has a first node which transmits on a data bus messages each having a preamble having a predetermined format including a message type and the message length, and a plurality of second nodes receiving messages from the data bus and including elements which can determine that the preamble in each message has the predetermined format. The preamble is particularly useful for allowing the second nodes to quickly detect messages not directed to those nodes of which the elements form a part, allowing the node to ignore the remainder of the message. This allows the individual nodes to exclude the message interpretation for detecting message directed to them, from their processing tasks thereby improving the effective processing speed of the network.

Abstract: A distributed environmental/load control system comprising a thermostat operable to supply signals indicative of sensed and desired values of a parameter in an environmentally controlled space to a first controller operable to control condition changing equipment for regulating the parameter, the signals being transmitted over a communications link between the thermostat and first controller. A second controller which is operable to control a plurality of loads in accordance with predetermined criteria to limit energy consumed by the loads is connected to the communications link through an interface device operable to process the signals produced by the thermostat in response to instructions furnished by the second controller and to supply the processed signals to the first controller.