Monitoring plural process control stations

DETAILED DESCRIPTION We claim: 1.
A monitoring system for process controllers with error recognition and compensation in a monitoring function comprising: a plurality of self monitoring process control stations, each including (i) a first and a second internal bus section interconnected by a redundancy coupler (ii) a central processing unit and an operating memory connected to the first section, (iii) a first and a second buffer and additional peripheral facilities connected to the second section, the first buffer containing a currently valid continuously updated representation of the process portion as controlled by the respective station the representation being produced pursuant to self monitoring, the second buffer containing a similar kind of representation of the process portion as controlled by the respective station and having resulted from self monitoring at an earlier point in time; a redundancy station including a central processing unit and a memory; coupler means for connecting the redundancy station to all said second bus sections; and the redundancy station assuming control of the operation of a process control station found to be defective by deactivating the respective redundancy coupler under utilization of the contents of the second buffer for continuing the process control function of the defective process station.
2.
A monitoring system as in claim 1, said redundancy station operating for cyclically monitoring the operational state of the process stations of the plurality by being sequentially coupled to the process stations of the plurality through said coupler means, said redundancy station causing the content of the first buffer to be copied into the second buffer pursuant to the monitoring controlling function during each monitoring cycle.
3.
Monitoring system as in claim 2, wherein the coupler means monitors the operating state of the redundancy station whenever the respective process station is coupled thereto pursuant to the monitoring cycle and in the case of detecting an error, the redundancy station is blocked from further accessing the particular process station