Wikipedia:Reference desk/Archives/Computing/2016 December 19

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December 19

Multiple cellphones on the same number

Today's edition of my local newspaper had a story about the relationship between Donald Trump and US congressional leader Paul Ryan, noting that the two will often speak on their personal cellphones for up to an hour. Now obviously Trump isn't taking cell calls from anyone except important figures, but still, it seems risky to spend so much battery on a single call when presumably there are other pieces of telecommunications equipment available for the president-elect. With this in mind, I'm wondering if it's possible to set up a system whereby multiple physical phones have the same number — from a technical perspective, is it possible for Trump's staff simply to plug one phone into a charger while another one, now done charging, is activated and begins getting calls instead of the other one? Nyttend (talk) 04:56, 19 December 2016 (UTC)

You could just swap the sim card to a different phone. Alternatively, you could swap the battery out (on a cell phone with an easily removable battery). Either of these would result in a few seconds of the cell phone being unavailable to receive calls. Finally, you could plug the cell phone into a power bank even while talking on it, which results in no down time at all.-gadfium 05:13, 19 December 2016 (UTC)

(ec) Wouldn't it be easier to just swap in a fully charged battery ? (Assuming it's not a model which prevents all access to the battery.) StuRat (talk) 05:14, 19 December 2016 (UTC)

Good ideas; thanks! Talking while plugged in came to mind (but I've never heard of a powerbank before), but I know I find it inconvenient to be tethered to the power outlet when talking on the plugged-in-and-charging cellphone (at least with a landline, you put it in a convenient place for talking, which isn't always the case with power outlets), and presumably Trump is much more mobile than I and doesn't have time for standing around by the outlet. I didn't know about the SIM card swap (I've heard of SIM cards before, but I figured they were competitor with SD cards), and I had no idea that it was possible to charge cellphone batteries when they're not inside the phone. Nyttend (talk) 05:48, 19 December 2016 (UTC)

(edit conflict)Trump probably would not be using a SIM card, as America normally uses them in pay-as-you-go plans, which are not targeted toward people who think a million dollar loan is small.

Some power banks are only slightly larger than a phone battery and can be carried with the phone in hand. Mine is about twice as thick as my smartphone, and theoretically (haven't gone this far) should multiply my battery life by five or six times while watching movies at full brightness. As it is, I charge the powerbank about once a week and use that to top off my phone before bedtime and whenever the battery is about to die. Ian.thomson (talk) 06:10, 19 December 2016 (UTC)

Could you expand on what you mean by that first sentence? I was under the impression that a cellphone must have a SIM card in order to connect to a network. Akld guy (talk) 11:29, 19 December 2016 (UTC)

Yes, you are entirely correct. Ian may be confused, because you only regularly exchange SIM cards when you buy them for relatively short-term use. If your phone comes with a contract, the SIM card goes in once (or may even have been put in by the carrier, possibly even SIM locked). But every device that accesses one of the standard cell phone networks (even Iridium) needs a SIM card. There are some attempts to move to an embedded, programmable SIM functionality, but this is not yet on the market for any phone I'm aware of. --Stephan Schulz (talk) 12:00, 19 December 2016 (UTC)

Thanks. There is another possibility: cellphones don't need a SIM card to access Wifi, so an owner could make calls via internet message and calling services such as Skype, with no SIM card. This might even answer the OP's question: log out of Skype on one cellphone and log in using the same username on another. Akld guy (talk) 12:15, 19 December 2016 (UTC)

The Casio G'zOne Ravine 1 does not have a sim card. (The Ravine 2 does) --Guy Macon (talk) 12:11, 19 December 2016 (UTC)

The sim card in the Ravine 1 is under the battery and, assuming it hasn't been touched from the factory, usually behind a piece of blue tape. There are many phones which have sim cards that are not designed to be removed, so they are buried in the phone. 209.149.113.5 (talk) 12:16, 19 December 2016 (UTC)

(Started typing this in response to Akld guy's first post and Stephan Schulz, dug up the last American phone just to verify that I'm correct here). Let me rephrase that: Trump would probably not be using a phone that lets you see your SIM card, let alone swap out. Most American cell phone models that let you swap out the SIM card are pay-as-you-go and targeted toward working class folks, while models for monthly subscriptions tend to embed everything so deeply that many require tools just to swap out the battery (and a few won't even let you do that without voiding the warranty). Ian.thomson (talk) 12:50, 19 December 2016 (UTC)

But what sort of phones are you talking about? This list [1] for the US has 4 iPhones and a Galaxy S5, none of which make it that hard to remove the SIM (ignoring carrier locks). Some may require a paperclip (or preferably I guess tool the manufacturer provides) or in some cases a fingernail or similar, but that's about all. This list for the US is a bit questionable since it relies on AnTuTu benchmarking [2], which explains why the iPhones don't show up, but none of those phones have SIM cards which are particularly hard to remove. Notably most of those phones are the sort of things you'd expect people with monthly subscriptions to use. The models targeting the PAYG are probably the iPhone 4, Nexus 5X and Oneplus.

Note also that while the may be some correlation between phones with easy to swap batteries and easy to swap SIM cards, many phones with non-removable batteries have easy to swap SIM cards. iPhones are an obvious example but most recent Nexuses are another. And I'm currently using an Alcatel Flash 2 which doesn't have an easy to remove battery [3] (even though ironically you can take off the cover and see it) but does have an easy to remove SIM card.

One of the obvious point is that in the modern UMTS & LTE & smart phone world, the majority of phones popular in the US are also likely targeted at other markets including in places where the lack of an easy to remove SIM is likely to be a killer. Sure, the phones sometimes have some minor modifications for different markets, most commonly in supported bands but these normally aren't so extensive as to make removing the SIM card difficult. Actually probably the most extensive modification is a dual SIM variant for Asia and I think a few parts of Europe. And the carrier can always lock the phone if they don't want people removing the SIM so there's limited point anyway. (Admittedly a software lock normally isn't that hard to remove but still, most aren't that concerned.)

I don't know if Trump is that into smartphones but he is into Twitter. And it's perhaps worth remembering the unmodified version of Obama's (in?)famous BlackBerry 8900 [4] also had an easy to remove SIM card. No idea of course if this applies to the secured version Obama had. And the unmodified version of his new phone the Galaxy S4 has an easy to remove SIM. Although again, this may not apply to his secured version. Mind you, I suspect by now Trump can't just use an off the shelf phone either but he does like to do things his own way, so who knows?

Nil Einne (talk) 13:28, 19 December 2016 (UTC)

(edit conflict)This source is a bit old, but it's pretty accurate (it's also somewhat reinforced by [5], [6], [7], and anecdotally by [8]). I tried looking up instructions accessing the battery or SIM card on the last model I had (LG Optimus G), and any instructions for removing the SIM card are for international models and not written by anyone who has seen the model I have right in front of me. Many phone manufacturers do indeed make different models of the same phone for different markets: The Samsung Galaxy Note 4 I have in the shop is dual SIM (Chinese, N9100), but the European model (N910F) is single SIM. Also, "most popular models" would be informed somewhat by working class purchases as well as international purchases. Of course, I've been out of the US for a year and a half, and last time I went phone shopping before then was a few years ago: maybe there's been a huge shift to accessible SIM cards in the past four years, but there wasn't when I was there. Ian.thomson (talk) 13:44, 19 December 2016 (UTC)

Those sources seem to be referring to CDMA phones. I was under the impression even they weren't so bad now (especially ones which also support LTE), but perhaps I'm wrong. However even if it's true, it seems it would only refer to a bit over half of US mobile phone subscribers [9] rather than exclusively a prepaid vs postpaid issue. Nil Einne (talk) 14:27, 19 December 2016 (UTC)

Of course I'm an old fart, and am still using an iPhone 5S, but that was certainly a premium phone when I bought it. To change the SIM, you simply poke something thin and reasonably strong (either Apple's special tool that came with the phone or the end of a paper clip) into the small hole on he right side, and out comes the tray with the SIM. Trump apparently uses a Samsung smart phone, and for the Samsung Galaxy S7, the procedure is very nearly the same as for my iPhone. Being able to easily change the SIM card is a valuable feature for world travellers, as you can easily plug in a local prepaid card, instead of paying high roaming costs, especially for data. --Stephan Schulz (talk) 13:25, 19 December 2016 (UTC)

My family's an Android family. I was familiar with the paper clip hole on my American phones: they held the reset button (and if you left it in too long, there was the risk of resetting everything but the carrier data). And most Americans who travel are used to paying too much for various services. Ian.thomson (talk) 13:50, 19 December 2016 (UTC)

(EC) My impression is that the onlyold CDMA phones used in the US didn't generally have something you'd consider a SIM. Of course it does depend what you consider a SIM since they did have a unique identifier of some sort but I don't think it was really designed like a SIM. This seems to be supported by Subscriber identity module#Usage in mobile phone standards. I don't believe analog mobile phones whether in Europe or elsewhere generally had something you'd consider a SIM either. Modern US phones and networks do have SIM/UICC cards. BTW [10] suggests one or more Apple devices does have an embedded SIM (in addition to an removable SIM). Our article mentioned above also seems in need of update. I presume the 2015 plan either happened or didn't. Nil Einne (talk) 12:52, 19 December 2016 (UTC)

I wonder if it is possible to have two cell phones on the same number for the purpose of having a spare. This would be for the situation where a phone is lost, stolen, or broken, and the spare would normally remain turned off. Could you clone the sim card so that the carrier could not tell which phone was in use as long as you never power up both at the same time? --Guy Macon (talk) 14:26, 19 December 2016 (UTC)

The cell phone companies won't allow that, as they would risk both being on at the same time, which would cause problems with their system. I have a spare "burner" phone, not activated. If my primary phone dies, my plan is to activate the spare and transfer the phone number (and also days and minutes) from the old phone to the new (most companies will do this for you if both phones are on their network). In my case, the spare phone is the same model, so I can also swap batteries and use the spare phone to charge the dead battery. Since my cell phones cost $5 each, that's no big deal, but if you buy $700 cell phones you probably don't want to do this. StuRat (talk) 16:02, 19 December 2016 (UTC)

It is within the realm of possibilites and called phone cloning (technically, it is more SIM cloning). Whether it is technically easy or legally permitted is another matter entirely. Tigraan^{Click here to contact me} 16:08, 19 December 2016 (UTC)

We are talking about Donald Trump and the US government here. There are lots of options available if you have resources and are willing to spend money. For example, even at the low-cost consumer level there are services, like Google Voice, that allow calls to a specific number to be forwarded to multiple devices (each having their own private number). At the professional level one can just as easily have several identical devices and a system set up to forward all calls to whichever phone(s) are active at the time. Each phone would internally have its own phone number and SIM card, but from an outside perspective any of them could be reached by dialing the main contact number. Presumably an assistant would actually be responsible for managing the phones, ensuring that at least one is charged at all times, and that Trump avoids any unwanted phone calls, etc. Dragons flight (talk) 16:58, 19 December 2016 (UTC)