H11-811 · Question #42
If the LOS indicator () on a board of the IP PBX, signals are lost.
The correct answer is A. Is on. LOS stands for "Loss of Signal" - it is an alarm indicator, and like most alarm lights, it activates (turns ON) to alert technicians that something is wrong, specifically that the board is no longer receiving a signal. Why B and C are wrong: An indicator that is off would mean…
Question
If the LOS indicator () on a board of the IP PBX, signals are lost.
Options
- AIs on
- BIs off
- CBlinks
How the community answered
(25 responses)- A76% (19)
- B8% (2)
- C16% (4)
Explanation
LOS stands for "Loss of Signal" - it is an alarm indicator, and like most alarm lights, it activates (turns ON) to alert technicians that something is wrong, specifically that the board is no longer receiving a signal.
Why B and C are wrong: An indicator that is off would mean the circuit is in a normal, non-alarm state - no fault detected. A blinking LED typically signals a different condition, such as an intermittent fault or an active/synchronizing state, not a complete signal loss.
Memory tip: Think of it like a fire alarm - the alarm sounds (turns ON) when there's a problem. Similarly, the LOS light turns ON when the signal is gone. "LOS is ON = Signal is gone."
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