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I'm writing a story about people being stuck in a large hotel. One character wants to call a loved one, but I'm trying to think of a reason that they can't. My initial thought was that the front desk line needs to remain open for communication with authorities, but I don't see a reason why they wouldn't just use their room's phone.

My research so far has indicated that phones work even during power outages. Is there a reason that the main desk phone would work, but a hotel's room phones wouldn't? Most hotels I have been at require you to dial "9" before calling out. Could this play a factor?

I'm also open to suggestions on how the hotel management could communicate with local government without phones, if I had to completely "cut the wires".

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    $\begingroup$ I don't see this as world building. Instead, it's "fact checking". $\endgroup$ – RonJohn Sep 11 '18 at 7:47
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    $\begingroup$ @RonJohn More like reality check $\endgroup$ – AntiDrondert Sep 11 '18 at 10:29
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    $\begingroup$ Welcome to the site, Chris. Please note that the Worldbuilding SE is dedicated to providing detailed answers to specific questions you have while developing your fictional world. This appears to be, at best, an issue for your story to resolve, placing it outside our scope. Not to sound snarky, but have you tried asking the desk clerk at a local hotel? $\endgroup$ – Frostfyre Sep 11 '18 at 12:50
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Maybe yes and maybe no

  • Old-style analog telephones are powered by the telephone network; old-style urban telephone networks (the so-called POTS, Plain Old Telephone System) generally have a power reserve of 48 or 72 hours.

    • Some (most likely old and formely Soviet) hotels may have their room telephones connected directly to the analog urban telephone network. (The last time I met with such an arrangement was some 15 years ago in Kishinev, Republic of Moldova.)

    • Other old hotels may have their internal analog telephone network; this is not unheard of even today. If the hotel has its own internal analog telephone network, its PBX (Private Branch eXchange) may or may not have reserve battery power.

  • Modern hotel room telephones are really small computers, likely using ARM processors and running some sort of voice-over-IP software. This kind of telephones are powered from the wired Ethernet network and are connected to a server. This kind of setup may or may not have reserve battery power.

    • In corporate settings the phone and data networks are just about always set up with a massive UPS (Uniterruptible Power Supply) and a Diesel generator.

    • In a hotel setting, it depends. Higher-end hotels will likely have UPSs. In some locales where blackouts are frequent, a Diesel generator may also be present. Mid-range and lower-end hotels likely wont' have reserve battery power.

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    $\begingroup$ Don't forget that even if the hotel has a UPS (which in turn can be backed by something like a diesel generator; "UPS" is a really broad term, and battery backup is one way to provide a short-term UPS), the problem may lie outside of the hotel's control. For example, especially but not exclusively if the hotel uses VoIP telephony, a problem on the other side of the city (or even farther away) can easily cause disruptions that show as the phones "working", but an inability to place any calls, unless the hotel has taken specific preparatory steps to deal specifically with such an eventuality. $\endgroup$ – a CVn Sep 10 '18 at 17:28
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    $\begingroup$ Good fairly thorough answer. However, not all places do "all or nothing" power backup. I worked at a place before where only the most critical hardware was backed up by UPS. This included network switches and servers, but for per-desk hardware only that of high level executives, IT (to manage what is still going), and the front desk remained on. Everything else blacked out immediately. $\endgroup$ – Loduwijk Sep 10 '18 at 20:12
  • $\begingroup$ @Aaron Your comment is based on a IT office, whereas this answer points out phones in a hotel. IT offices require UPS for hardware whereas hotels more or less prioritize comfort, style, food over IT hardware. $\endgroup$ – Mr.J Sep 11 '18 at 0:28
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    $\begingroup$ Add in a minor server room fire/breaker trip due to a bad relay/failed undercharge protection/bad extension cord connected to the ups/accidental paperclip dropped into a loose connection and you could cover all your bases. $\endgroup$ – Nonny Moose Sep 11 '18 at 0:52
  • $\begingroup$ Don't forget that, even though the hotel might have a UPS and as such keep the phones on, the server might not. As phones nowadays run like you say, it requires more than just the phone being turned on. If the route in between gets interrupted (Internet Service Provider (ISP), Domain Name Service (DNS), exchange boxes, (undersea) cables, etc etc) it still all stops. In case of black-out you're best bets are probably shortwave muscle powered (wind-up) radios $\endgroup$ – rkeet Sep 11 '18 at 12:48
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Regular phones work during outages, but servers which route calls will only last as long as the batteries on their UPS. It may be that the front desk phone is connected to a regular line and the hotel's internal PABX or equivalent; all room phones need to go through a server to reach the proper phone company lines. When the servers are down, you are out of luck.

This is specially true nowadays, given that we are using increasingly more VoIP solutions.

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    $\begingroup$ I know some folks that own a hotel in an area prone to power outages, and this is exactly the situation they see. The phones themselves can technically work without power, but the PBX they connect to goes down so the phones are effectively useless. Only the phones directly connected to the outside line are still usable. $\endgroup$ – bta Sep 10 '18 at 21:55
  • $\begingroup$ This greatly depends on the kind of phone. Digital phones, still common in (lower end) hotels in the US, require "phantom" power that is provided by the PBX and will not even offer dial tone if the PBX has no power. PBXes are not generally called "servers" in the phone industry (they might be called "switches"). IP phones also require power, but their power more often comes from network switches that provide power over Ethernet (PoE). If the Ethernet switches are up but the IP gateway/server is down, then you could get dial tone on the phone with no ability to make calls. $\endgroup$ – Todd Wilcox Sep 11 '18 at 14:22
  • $\begingroup$ @bta Technically, there is no phone in the world that works without power. Even the old analog kind that is connected directly to the phone lines is actually getting power all the way from the phone company (often called "battery"). If a phone has lights, display, dial tone, touch tones, etc. that are working, then the phone is receiving power. If you can't make any calls despite the phone power, then that means some upstream device (PBX, VoIP gateway, key system, etc.) does not have power or a communication line is cut. $\endgroup$ – Todd Wilcox Sep 11 '18 at 14:24
  • $\begingroup$ @ToddWilcox I was trying to say that the phones would work if you connected them directly to the public phone system (that is, they don't require a separate power supply), and that it was the failure of the PBX that caused everything behind it to go down. $\endgroup$ – bta Sep 11 '18 at 17:55
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Home phones continue to work because they get their power from the local exchange. The local exchange gets their power from the same source you and I do, but usually the reason causing your blackout does not affect the power going to the exchange.

I worked in a restaurant attached to a ten-plex hotel. When the power went out the room phones did not work because they got their power from the PBX and when the PBX went down there was no power for the phones. The front desk phone also went through the PBX, but when the PBX lost power or had some other kind of error the front desk phone was able to bypass the PBX and connect directly to one of the phone lines in the trunk -- the one to which our primary phone number was provisioned.

So if you need the room phones not to work you can simply provide for no backup power to the local PBX. You don't have to explain it, just say "the only phone which works during the blackout is the front desk phone".

I hope that helps.

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    $\begingroup$ Local exchanges have batteries, so the phones continue to work even through widespread power outages. $\endgroup$ – prl Sep 11 '18 at 4:34
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These days a lot of hotels have cordless phones in the rooms, these absolutely require mains power to their base stations to continue operation and will crash in an outage. For anything else it depends on the set up of the internal network hardware and reserve measures, if any, included therein.

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  • $\begingroup$ Well, I think you don't really need to go on with the “anything else”. They need a way to make their scenario work, and this answer provides exactly that. I upvoted because it is a simple and easy way to resolve — however … What if a guest decided to walk away with the phone? They could always charge them for the replacement, yes, but the overhead of time required to restock on them and to get a new replacement in the room during room service seems like a bit much. $\endgroup$ – can-ned_food Sep 10 '18 at 23:25
  • $\begingroup$ @can-ned_food That's why hotels/motels here only take bookings with credit cards attached to them, you better leave the phone in your room where it belongs when you leave. But I know at least a couple of the places here in town actually have a stack of room phones, new in their boxes, in the cupboard behind the front desk so it must still be an issue sometimes. $\endgroup$ – Ash Sep 11 '18 at 10:43
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The typical home phone continues to work because it is drawing its power through the phone line, which is getting it from the phone company exchange. I presume the phone company normally has backup generators so they can keep working through a power failure. If you want to make such a phone fail for purposes of your story, all you need do is say that the backup system at the phone company failed.

Years ago most hotels (and mid-size to large businesses) had a PBX, "private branch exchange", to connect all the room phones to each other and to outside lines. Maybe today many or most are using VOIP, "voice over internet protocol". Either way, these require local power to run the PBX or server. The hotel may have backup power, or not.

If they have their own backup power, the idea of that failing is not wildly implausible. I used to work for a company with a chain of retail stores. The stores were all connected to headquarters over the internet. They were very worried about the servers going down and the stores being unable to process sales. So they built a "bunker" that could survive a tornado, fire, etc to house the servers. Then the servers had a battery back up that kicked in automatically in case of power loss, a generator to back up that, and a second generator in case the first generator failed. A few months after putting all this together, there was a power failure. The battery backup failed, the first generator failed, and the second generator failed. Our servers all went down.

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Too many calls

So, there is a power outage. Everybody and their uncle grabs the room phone to 1) ask what is going on or 2) tell somebody about it.

Unfortunately the local network is not scaled for this. Even if there are battery backups all over the place, the system can NOT handle that many calls at once.

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Have you considered a lightning strike? Could conceivably burn the internal hotel network, but leave the external connections intact.

More trivially, if your setting is in modern times the internal phone system could just crash due to software or hardware problems. Might be even a malicious hacker attack, if it works for your plot.

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PSTN phones get their power from the exchange they're connected to. Large exchanges (like your local one) have battery and generator backups - that's why your phone continues to work even though there is no power in the whole city.

Hotels (and large offices) are bit different. They have small local exchanges - that's why you have to "dial 9" to reach outside network. If the hotel exchange doesn't have backup power (a reasonable expectation), all phones connected to that exchange will go quiet with it. If the front desk phone can reach room phones directly, it's hooked up to the hotel exchange and depends on it as well. However, it's possible that the front desk has a second phone, one connected directly to the outside line - and this one will keep working. Another possibility is that the local exchange has a failover mode: when it loses power, it connects one, predefined phone directly to the outside line.

Bottom line: if you want the hotel phones to die, just kill the local exchange in the basement. Front desk can have a second phone, according to your needs.

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