A microcomputer controlled monitoring system and method for detecting an electrical open, shorted or operative condition of an electrical load. A load switch circuit couples the load to a common voltage line and is controlled by a single drive line from a microcomputer controlled load monitor circuit.

A microwave oven includes a plurality of magnetrons for cooking purposes. When at least one magnetron is placed in a fault condition, an indication lamp is enabled to display the fault condition. When the cooking operation is interrupted by opening the oven door while the cooking operation is performed, the indication lamp is held in the former state. That is, when the oven door is opened under the normal operation mode, the indication lamp is never enabled. When the oven door is opened under the condition where at least one magnetron is placed in the fault condition, the indication lamp is continuously enabled to continuously display the fault condition.

Control circuit system wherein low level signals are delivered through small (miniature) gauge control conductors to remote control circuit breakers to control connection of load devices to load bus through use of solid state circuitry. Such control may be used between the flight station of an aircraft and the various load centers remote therefrom, in an automobile or in an industrial or utility system. The circuitry is also responsive to faults in the load circuits, and current limiting warning lights (CLWL's) located in the power supply of the control conductors may limit current and indicate the status of faults in the control and/or remote power circuits. A large number of CLWL's for the different circuits may be arranged in a matrix at a control station and means with corresponding load identifying indicia are provided to facilitate changes and correlation of lighted CLWL's with respect to the controlled load switching device. The load switching devices may be associated in a plurality of priority groups and means provided to disconnect all the devices in a group simultaneously either manually or sequentially in reverse order of group priority upon increasing power system failures or in response to other control logic.

An automatic recycle circuit is disclosed for use in a process or apparatus of the type wherein process or equipment conditions are monitored to detect an abnormal condition. The automatic recycle circuit accepts inputs from monitor circuits which are intended to cause recycle operation and monitor circuits which are intended to cause complete shutdown and reacts appropriately to each type of input. With respect to those inputs from monitor circuits which are intended to cause recycle action, the automatic recycle circuit is capable of permanently shutting down the process or apparatus if the detected abnormal condition has a duration exceeding a first predetermined time or abnormal conditions are detected a predetermined number of times within a second predetermined time period.

A microcomputer utilizing a crystal controlled clock and a power line responsive clock operates both the control system and into a safety timing means. The safety timing means can take the form of a pair of retriggerable monostable multivibrators that are operated to monitor the microcomputer along with a feedback circuit from a load control means. The feedback from the load control means senses the status of a safety switch means and provides the microcomputer with the ability to monitor and be monitored for safe operation.