topic Re: Red alarm light won't go off in Broadband

Red alarm light won't go off

Gary_66 — Fri, 19 Dec 2025 07:50:13 GMT

I have tried switching the power off but red alarm light is still on.

Re: Red alarm light won't go off

Chrisee — Fri, 19 Dec 2025 08:00:20 GMT

@Gary_66 the alarm light on older ONT units is triggered by the failure of the built-in battery back up unit which these units included to allow a digital phone connection during a power failure. This facility was never used in practice and newer units dont have the battery at all . It is therefore safe to ignore but if it annoys raise it with Sky as it can be bypassed or a newer unit fitted.

A red LOS light however indicates a fault.

Re: Red alarm light won't go off

JimM1 — Fri, 19 Dec 2025 10:07:05 GMT

@Gary_66 Also depending on which ONT you have, the Adtran model first left led is also marked as alarm and has the similar function to the LOS, Red on any ONT is not good, and it may require you to call sky to have it looked at!