Quality of Alarm Source's value at the moment of this Event. This is a read-only property. Possible values for this property are 0 - 63: Bad quality, 64 - 127: Uncertain quality, 128 - 191: Undefined value, or 192 - 255: Good quality. If this Event is not an Alarm, this property is equal to an empty String. Examples of this property's content are "Bad (0)", "Uncertain (64)", "?? (128)", or "Good (192)".