This gauge counts the total seconds of loss-of-signal events from midnight to now, where the equipment physically loses the ability to detect an incoming signal. A network engineer immediately escalates high LLOSS counts because they indicate a physical-layer catastrophe (cut fiber, bad connector, power loss) that makes the circuit completely unusable. For example, 10 seconds of loss-of-signal in a day means the link went down for short bursts and needs hardware troubleshooting.