Abstract: Messages at nodes of a distributed data system are processed asynchronously. Each data atom shared by a pair of nodes is characterized by dipole halves maintained at each node including an access control characteristic, a quality control characteristic, and a pair of rank values. A rank value is a value which monotonically increases (with respect to time) with each significant event. A message from a paired node requesting a change to a dipole half at this node includes the set of rank values at the paired node for the shared data atom. This node compares the rank values which it maintains with those received from the paired node and, based upon the result, selectively rejects or processes the request.

Abstract: A soil pollution monitoring system includes a plurality of ducts for conveying gases and air past a sensing device. The sensing device detects selected compounds in the gases and air and provides an output in electrical form which indicates whether or not the levels of certain compounds in the gases and air are greater than a threshold amount thereby indicating that a leak has occurred.

Abstract: A method for dynamic replication of data under distributed system control to control the utilization of resources in a multiprocessing, distributed data base system. Previously, systems providing for data replication at nodes of a multiprocessing, distributed data base system required that a central node maintain control, or that replicated data be synchronized by immediately conforming all copies of an updated data item. By this invention, requests for access to data of a specified currency are permitted and conformation of updated data is selectively deferred by use of a control procedure implemented at each node and utilizing a status and control (SAC) filed at each node which describes that node's view of the status for shared data items at other nodes.

Abstract: A low liquid level electro-optical probe is made self-checking by providing the same with means for intercepting a portion of the usual light beam and constantly reflecting such portion to the usual receiving electro-optical transducer to constantly generate a low level electrical signal even when the probe is wet. Means are provided for boosting the signal to activate an alarm, failure of which will be indicative of failure or malfunctioning of one or more elements of the system.

Abstract: A circuit for allowing an air conditioner to be installed in a motor vehicle using the vehicle's existing heater and vent controls. A slide potentiometer is attached to the heater control arm that normally controls the heater air temperature. The slide potentiometer has two resistance elements electrically separated from each other, but only a single wiper that moves from one to the other as the arm is moved. The air conditioner and heater have separate blowers, but both are connected to the conventional heater blower switch. A relay is connected to the heater and air conditioner blower circuits for enabling either one or the other to operate. The relay is actuated by a switching circuit that is completed only when the wiper is in contact with one of the resistance elements and not the other. Another enabling circuit is completed when the slide potentiometer wiper is in contact with the other resistance element. This latter circuit enables the air conditioner temperature regulating circuitry to function.