There are two types of alarms: level alarms, and trip alarms.
• Trip Alarm: A trip alarm is triggered when the value of the alarm tag changes from a "0" to a "1", and will not return to a normal state until the alarm is cleared by the operators of the system, and the equipment process that caused the alarm to trigger is reset (in other words, once triggered, the alarm remains active until it is manually reset, even if the condition that triggered it no longer exists.)
Trip alarms are used only with digital tags as their triggers.
• Level Alarm: A level alarm is triggered when the value of the alarm tag changes from a "0" to a "1", but will return to a normal state on its own if the condition that caused the alarm to trigger returns to a normal state either by operator intervention, or on its own (in other words, a level alarm remains active only as long as the condition that triggered it exists.)