Possible combinations
The alarm inhibit bit (indicated with the | symbol) can be set as follows:
From PC set
An inhibit bit from the PC makes it possible to inform the PLC about the alarm inhibit state of the object.
To PC set
An inhibit bit to the PC allows the PLC to control the inhibit state of the object. This is in principal the same action as if the operator inhibited the alarm manually.
Both To PC and From PC set
If an inhibit bit is set both to and from the PC a "handshake" situation exists, where the PC sends the alarm inhibit information back to the controlling PLC.