You can use the Dial In Overactive feature to alert users whenever a PSTN outstation is dialing in excessively.
When you configure the Dial In Overactive feature for a PSTN outstation, you define a dial in limit and a time period. If the number of times the outstation dials in during the defined time period exceeds the dial in limit, an alarm is raised or an event is logged. The alarm or event indicates that the outstation is dialing in too frequently. The possible reasons for a PSTN outstation dialing in too often include:
- A high number of alarms being raised or cleared
- A log (or buffer) filling or overflowing
- Scheduled dial-ins configured to occur too often
- Excessive use of the Callback feature
- The outstation requires configuration.
Some of these conditions may be due to incorrect configuration at the outstation, for example, there may be a high number of alarms being raised because of poorly configured alarm limits (and other alarm limit related settings, such as Persistence).
When an alarm is raised as a result of the outstation dialing in too frequently, the alarm is added to the various Alarms displays, including the Alarms List and Alarm Banner.
The alarm has the following message:
Too many incoming calls (# calls in less than <interval>)
Where:
- # is the number of incoming calls
- <interval> is the configured interval, for example, 1D.
The number of calls shown in the alarm message will be updated if additional incoming calls occur before the time period elapses. An event will be logged for each individual dial in and the alarm will clear automatically at the end of the dial in time period.
A dial in call is counted at the end of the call and so an alarm is only raised when the call has been completed. All incoming calls are counted, including any calls that are deemed to have failed (providing that the driver can identify which outstation made the call). Some drivers do not count text message calls. For further information, please refer to the driver documentation.
You can view the number of dial ins that have occurred during the current time period by accessing the Status display for the required outstation. (The Status display is sometimes referred to as a View window or View dialog). The number of dial ins is shown next to the Dial In Overactive entry and shows the number of incoming calls in the current time period and the maximum number of calls.
A PSTN outstation is scheduled to dial in once per day. Under normal circumstances, the outstation would be expected to detect between 0 and 9 alarm conditions per day.
The Dial In Overactive feature is configured for the outstation. This sets the outstation to have a limit of 10 dial ins per day (1 scheduled dial in and a maximum of 9 dial ins related to alarm detection). If the outstation dials in more than 10 times in a day, an alarm will be raised to indicate that there is an excessive number of dial ins.
The outstation detects 11 alarm conditions in 6 hours. This causes an alarm to be raised that informs users that the outstation is detecting an excessive amount of alarms. This may be due to a genuine problem on site that is causing a high number of alarm conditions or may be the result of incorrect configuration on the outstation. An engineer responds to the alarm by acknowledging it. The alarm remains uncleared. If there are any further dial ins, The number of calls shown in the alarm message will be updated and an event will be logged for each individual dial in.
An engineer investigates the alarms being detected by the outstation and determines that the problem is caused by incorrect alarm limits being configured at the outstation. The engineer corrects the configuration and the alarm is cleared at the start of the next dial in time period.
To configure the Dial In Overactive settings for an outstation, see Define Dial In Overactive Properties on a PSTN Outstation.