This read-write Gauge sets how many Unavailable Seconds must accumulate in the near-end bucket before the device raises a Threshold Crossing Alert for the circuit; the factory default is 10. An admin lowers it to get earlier warning of DS3 line trouble (a value of 10 means the alert only fires once 10 unavailable seconds have been counted, since the circuit was considered unavailable, i.e. part of a run of 10 or more consecutive severely errored seconds).