Parent return-to-normal timeout

The parent return-to-normal (RTN) timeout value assists in suppressing child alarms that are held until after the parent returns to normal. This timeout value can be used either with or without a configured parent alarm timeout value.

In the figure shown below, if the child stays in alarm for a period of time after the parent returns to normal, then the parent RTN timeout is used rather than the parent alarm timeout. In this case, the parent alarm timeout is set to 0, which causes the indefinite suppression of the children alarms while the parent is in the alarm state. This timeout value is set so that child alarm reevaluation is made after the parent has been in the normal state for the timeout duration (for example, 80 seconds).

The parent RTN alarm suppression timeout can be used in combination with the parent alarm suppression timeout. The above figure shows both timeout values configured. In this case, the parent returns to the normal state and the RTN alarm suppression timeout extends the suppression interval. As the child returns to the same state it was in at the time of suppression, the system will not generate any child alarms. If the parent stays in the alarm state for more than 40 seconds, the RTN timer is not triggered; the system reevaluates the child and, consequently, generates an alarm.

Notes: If only the RTN suppression is configured (for example, alarms are indefinitely suppressed while the parent is in alarm), then the suppression is cleared if the remote containing the parent goes stale due to communication failure or the remote being placed offscan.

Regardless of the configuration of the timeout values, the child’s state is compared to its state when the parent went into alarm after all timers have expired. The child’s alarm state is not reevaluated as each timeout value (or timer) expires.

The timeout values are not reset during transitions between alarm states or during transitions between normal states. The alarm suppression timeout value is cleared when the parent shifts into a normal state and after the successful setup of the RTN alarm suppression timeout. However, if the parent shifts back into an alarm state while the RTN timer is active, then the system will neither clear the RTN alarm suppression timeout value, nor set up an alarm suppression timeout value. This avoids the indefinite suppression of alarms when the parent toggles continuously between abnormal and normal states.