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Comment by tonyedgecombe | Hacker News Reader

I was in an elevator a while ago when there was a ringing followed by a voice trying to sell PPI services (a regular source of spam in the UK). The emergency system was just an embedded phone.

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In our university, some guy figured out the phone numbers of the phones in the elevators. Sometimes we'd dial that number and have a random conversation with a random person. Other times we'd dial and just listen in. Caught a few juicy tidbits of conversations between faculty, but nothing major.

Exactly the same at my university except the the phone in the lift would ring and have to be picked up by someone.

We'd wait until the lift was totally crammed with people, call it and then ask to speak to someone we knew was in the lift!

In the US too - the reasoning is that it's simple and should work in a power outage as the telephone company usually can power it from the central office. Conversely, VoIP would depend on too many technologies working well to be reliable enough for emergency use.

An interesting thing to think about in elevators is who exactly the elevator phone calls, as well. In large buildings it sometimes rings a location staffed 24/7, like a security desk. In most buildings, though, for better reliability the phone actually rings a dedicated outside answering service for elevator phones. Sometimes this is provided by the manufacturer of the elevator as part of an "all-inclusive" service package, and sometimes they're hired by the property manager, but in a lot of cases the elevator company that does the maintenance programs the elevator phones to call their contracted answering service so as to ensure that they'll be the ones sent out to do the repairs. It's a bit like the plumber leaving you a fridge magnet with their 24/7 line.

Yeah, I got stuck in the elevator in my apartment building and had to use the phone, it went to the local Otis service line.

I've definitely seen elevator phones attached to the PBX with VoIP trunking, but all the components were on battery backups.

At a previous employer (large .edu), we moved to VoIP several years ago but keep several PSTN lines -- including all of the emergency ones, such as for the elevator. We could have moved them to VoIP as well but we figured, in a true emergency, it was one less thing to have to worry about.

In Chicago building codes mandate elevators have a pstn line in place.

Even luxury homes with small elevators.

Well, I mean people have died from being stuck in their own elevators: http://www.cbsnews.com/news/elderly-couple-dies-trapped-in-h...

Most large cities' building codes mandate auto-start/auto-transfer backup generators for elevators in buildings over a certain height. It is sometimes possible to put critical equipment on a generator backed circuit (such as a 48-port 802.3af PoE switch providing power to phones).

This can be harder to do than it looks at first glance - the electrical cable "snake" that follows elevators up and down their shaft is frequently implemented with only POTS/cat3 grade wiring. Getting a SIP phone to work in one can require a local source of power in the elevator (usually a 120VAC to 12VDC power supply for the phone rather than PoE) and a VDSL2 bridge for 100BaseTX over the old style phone wiring.

Right, I'm talking about a plain analog phone connected to one of the ATAs on a Cisco PBX. I was doing some other work on the rack and remember a cable flag that said "ELEVATOR" :).

We seem to have a similar system in Poland. My friend was coming home once and the elevator started talking to him, trying to sell him some service. Following the moment of surprise, he managed to regain sanity fast enough to catch some of it on video.

Turns out the emergency system on this elevator is too an embedded phone...

Yep. That's standard. In a building with a PBX they are not typically assigned external numbers, but elevator phones are in general just like any other phone in the office. Maybe an automatic dial on going off-hook.

elevator phones are very very rarely on the PBX at all, and are for safety simply, local exchange lines.

An example of why. I once worked on a team tasked with auditing the phone lines in an office building to identify potential cost savings on lines with outgoing access.

We came across two on the PBX that no one could identify. Numbers not in the internal directory. No tags in the PBX terminal. Rang them repeatedly with no answer.

So we disabled them on the grounds that if they were in use we would soon get a call from someone enquiring why their line was dead. Nothing all week. Went home for the weekend.

You can probably see how this ended, and that's (just one of the reasons) why you don't route them through your PBX.

More like an example of how their provisioning and documentation process is broken, you can absolutely have critical things on SIP (and PoE powered security cameras, etc), just don't forget to document it correctly.

Sure. Absolutely. But if they'd been straight PSTN lines the abject process failure you've correctly described wouldn't have been able to put lives at risk because we'd have had to call the telco who most assuredly would have known what the lines were for, and we wouldn't have been able to shut them off. Safety critical systems need to not rely on humans doing boring, complicated things correctly for long periods of time.

> the telco who most assuredly would have known what the lines were for

yeah, about that...

Much more likely the telco would just have the business name for billing info for a POTS line and would happily shut it off.

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