If stop arming is not used, the Analyzer ends measurement when all requested samples have been collected. However, if signal is absent (or lost) on one of the inputs used for the measurement – timestamps from this channel will never come and Analyzer will wait forever unless measurement is stopped explicitly.
However, in many cases this is undesirable behavior. For example in an automated test system when absence of signal can be a result of a wrong test setup or device under test malfunction, it is would be a waste of time to wait until the expected end of a long measurement to discover that one of the signals is just missing.
This is where Timeout function comes to help. If Timeout is ON, the measurement will end in case there are no samples from one of measurement inputs for the time duration set by Timeout Time.