In order to perform some pick actions, such as a point Control, the Geo SCADA Expert server needs to be in communications with the outstation.
When such a pick action is requested for an item on a direct outstation on which communications is set to ‘Always’ and not ‘On Demand’, Geo SCADA Expert will immediately send that request to the outstation. If Geo SCADA Expert has detected that the outstation’s direct line(s) have failed and the outstation has PSTN fallback enabled, Geo SCADA Expert will execute a One Shot call to the outstation. The One Shot call sends the request to the outstation via PSTN.
With direct or PSTN outstations on which communications is set to ‘Incoming Only’ or ‘Periodic’, if such a pick action is requested outside of the available communications period, Geo SCADA Expert will automatically queue that request until communications is next established. (If the pick action is requested during a ‘Periodic’ outstation’s available communications period, but that outstation’s direct line(s) are down, Geo SCADA Expert will execute a One Shot call to the outstation. This will only occur if the outstation has PSTN fallback enabled and the direct line(s) are down during the availability period.)
With a PSTN outstation, if a call is in progress at the time, Geo SCADA Expert will immediately send the request to the outstation. If a call is not in progress, Geo SCADA Expert will execute a One Shot call to that outstation in order to send the request to the outstation.
With PSTN outstations and ‘On Demand’ outstations, it may be preferable to queue certain requests rather than have Geo SCADA Expert contact the outstation as soon as such a request is triggered. The same applies to direct outstations on which PSTN fallback is enabled and Geo SCADA Expert has detected that the direct channels have failed. For more information, see Optionally Queue Pick Action Requests on PSTN and ‘On Demand’Outstations.
Further Information
Direct and PSTN Communications.
‘Incoming Only’ and ‘Periodic’ communications: see Specify the Availability of Communications Between the Outstation and Geo SCADA Expert in the Geo SCADA Expert Guide to Advanced Drivers.