This read-only on/off attribute, defaulting to off, indicates whether a Section-layer Loss of Signal condition is present at the OC-3 port. It gives an administrator SONET-layer diagnostic detail below the general hcxOc3PortLOSLed indicator, pointing specifically to the section-layer signal being absent. For example, a technician troubleshooting an optical outage would check this attribute to confirm the failure is a section-level signal loss rather than a higher-layer framing or path problem.