topic Re: ONT Query in Everything else

ONT Query

pvmb — Mon, 20 Oct 2025 15:09:43 GMT

Does anyone know what the function of the 'Alarm' light is on the Openreach ONT (No. It isn't on!)

Re: ONT Query

jab1 — Mon, 20 Oct 2025 15:13:09 GMT

Yes - it indicates when there is a fault/break between the ONT and the 'outside world' - or in my case recently, a failure of the ONT itself. You never want it to go on. 😀

Re: ONT Query

MisterW — Mon, 20 Oct 2025 15:14:05 GMT

@pvmb I didnt know there was an 'Alarm' light on recent ONTs. IIRC on early ones with battery backup there was an ALARM on the BBU. Lights on mine are PWR, LOS, PON & LAN

Can you post a piccy

Re: ONT Query

jab1 — Mon, 20 Oct 2025 15:27:37 GMT

@MisterW My Adtrans ONT has 'ALARM' 'LAN' 'PON' 'POWER' left to right.

Re: ONT Query

pvmb — Mon, 20 Oct 2025 15:33:49 GMT

Here is picture of ONT. Could have turned it around I suppose. Sorry!

Just noticed from the photo it has its own ON/OFF switch.

Re: ONT Query

jab1 — Mon, 20 Oct 2025 15:36:57 GMT

And mine:

Re: ONT Query

Dan_the_Van — Mon, 20 Oct 2025 15:47:23 GMT

My ONT has a LOS LED, so maybe it's called ALARM on yours

EDIT: it normal status is OFF

Re: ONT Query

Townman — Mon, 20 Oct 2025 15:43:59 GMT

Images approved.

Re: ONT Query

MisterW — Mon, 20 Oct 2025 15:54:26 GMT

My ONT has a LOS LED,

Likewise

so maybe it's called ALARM on yours

That would be my conclusion as well

edit: although maybe not ?

on @pvmb s photo the PON is red, and on @jab1 s its green, whereas on ours the PON is only either GREEN or OFF.

so does the PON light handle both the PON and LOS functionality on later ONTs ? with the ALARM meaning someting else ?

Re: ONT Query

jab1 — Mon, 20 Oct 2025 16:05:02 GMT

@MisterW When my ONT failed the 'Alarm' light went orange. Talking to the OR engineer when he came, his first comment was 'I don't feel like going up ladders/down holes today' (with a grin), so he just checked my light levels and said 'they're good', fetched a new ONT, and 'hey voila' I was back up in 20 minutes or less, so I'm guessing the 'Alarm' is the 'LOS' light, renamed?

Re: ONT Query

Dan_the_Van — Mon, 20 Oct 2025 16:08:09 GMT

@MisterW

Looking at @pvmb it has no LAN cable connected either, so I'm wondering it the circuit is live?

Re: ONT Query

MisterW — Mon, 20 Oct 2025 16:12:03 GMT

@Dan_the_Van from other posts I don't think it is yet! There's been some confusion within OR ( nothing unusual there then )

Re: ONT Query

DerekW — Mon, 20 Oct 2025 17:20:38 GMT

That is what the lights on my ONT looked like, one red and one green, until I emailed the CEO of Openreach asking him to sort it... which they did PDQ.

The reason for my light being red was because there was a problem with the light at the exchange

The lights on my ONT, from left to right are, Alarm - LAN - PON - Power

LOS I believe stands for loss of service.

Re: ONT Query

jab1 — Mon, 20 Oct 2025 17:24:06 GMT

@DerekW wrote:

LOS I believe stands for loss of service.

Correct - now called 'Alarm', because, I'm guessing, it doesn't just cover loss of service, but other fault conditions, too.