One of the great mysteries to us non-Americans is the North American numbering plan for telephones. We’re exposed to it in films and TV shows, but how it works exactly is a bit is not obvious to us (at lest not me). For instance, in Germany, phone numbers don’t have a fixed length; they can have different lengths, based on how much phones there are in your area code.
But what I’m wondering about here is whether phone extensions for in-house systems are common in North America. In the company where I work, the entire company has the same phone number (under the local area code). Every employee working there has an extension of four or five digits. Outsiders who want to call me dial the number of the company and append the extension. Alternatively, they can also go through a switchboard with a human operator, which they reach by calling the company number plus extension zero, but if they know my extension they can use it to call me directly. If I want to call another employee from within the same system, I dial only the extension without the company’s number; if I want to place a call to the outside, I have to dial a zero (which tells the system that I want to get out of the in-house system) and then dial the usual number.
From my (limited) experience calling US numbers, I get the impression that people working in large companies have the standard seven-digit North American phone number, which does not necessariy bear any resemblance (other tahn the area code) to the number of a coworker sitting in the same building. Do extensions in the sense described above not exist, or do they and are simply not universally used?
Companies usually have a block of related numbers. My company had reserved 2000 numbers, 617-276-2xxx and 617-276-3xxx. The main number was +1617-276-2000 and the operator could connect you to extension 3478 or you could call 617-276-3478 directly.
I don’t think it’s the number of phones in an area code that determine the length of a phone number. When I was working in Kaiserslautern, my office phone and office fax numbers had different lengths, even though they had the same area code. (And whenever I had to give these two numbers to an American, they always tried to argue with me that I had made a mistake because one number was shorter than the other.)
The actual practice depends entirely on how the company’s phone system is set up.
With an IT background, I have seen both systems: ones where the inbound call has to go through the main gateway, followed by specifying an extension; and others where every desk has its own dialable number in the usual format.
In my experience, it’s a matter of when the company was established, how much they spent on their phone system, how wedded they are to their primary number, and other factors.
I think that such things typically happen when an area code grows in size. I grew up in a small town, and the phone in my parents’ house had (or rather, still has) a four-digit number - there simply wasn’t a need for longer numbers because there were few phones. In small villages, three-digit numbers used to be common. Meanwhile, that town also has six and seven-digit numbers, but my parents still retain their old four-digit number. So perhaps your phone and fax were assigned their respective numbers at different times.
In a way, this is compensated for by the fact that small towns tend to have shorter area codes than major cities - my small hometown has four digits (plus the preceding zero, if you dial in from elsewhere), the city I’ve meanwhile moved to has two (plus zero). But the sum of area code plus local number is still not necessarily the same for each phone.
Interesting, that sounds like a hybrid between the two options I had in mind: The individual numbers in the company are all directly dialable seven-digit phone numbers rather than extensions, but since they were allocated as a block, they all start the same.
Many companies have their in house exchange, commonly called a PBX (Private Branch Exchange) no matter how it is implemented. Traditionally this entailed a small number of outside phone lines that are shared by a large number of internal extensions. Other times a company may have a large block of outside lines that allow direct access through a 10 digit phone number, but depending on the availability of extensions and exchanges it can be difficult to reserve the numbers. There have been some hybrids of these systems but currently VOIP (Voice over Internet Protocol) is replacing the older systems.
Most companies will have either the system @Honolulu_Lulu described, with blocks of numbers, or a single ten-digit number for the company, with extensions beyond that (and when you call that ten-digit number, the robot voice will helpfully tell you “If you know your party’s extension, you may dial it at any time”). While a company could have completely different phone numbers for everyone, this isn’t common.
Often, there is some effort to coordinate phone extension numbers with something else, like room numbers.
That’s actually been the system at most places I’ve worked- there was a direct dial number for each extension but internally (including from the switchboard) , you could dial just the last 4 numbers. Where I am now, to transfer a call you have to dial the full area code and number.
Without exception a phone number is 10 digits (3 digit area code plus 3 digit local exchange plus 4 digit number). In some cases you can dial a number within an area code with only the last 7 digits, but sometimes you will need to use all 10 digits within, and in all cases across area codes.
Your area code- traditionally an entire state to one city, used to be kind of a shorthand for where you live with lower once being more prestigious, they were originally assigned to prominent cities due to being easier to dial on rotary phones. New York was 212, Chicago was is 312, But now larger cities have a bunch and people are using cell phones where you’re allowed to keep your area code when you move.
Businesses you may need to use an extensions, but more sophisticated systems at larger companies have virtual phone numbers- there may be 500 employees but only 50 trunk lines to the company, but it appears to the outside as 500 phone numbers.
This is how it works in the UK, as well (if that’s the service a company signs up for). We also have fixed length tel numbers. Of course these days everyone just has a company mobile, so the desk phones are all pretty dusty.
Seven-digit dialing used to be common, back when most calls most people would be making were in the same area code, and when there were few enough area codes that they could all have 0 or 1 as their second digit (and exchanges weren’t allowed to have a 0 or 1 there, so the phone system could always tell the difference). But then, cities started running out of numbers, so they had to introduce a bunch of new area codes, and so it became common for any given person to make calls to multiple area codes, and the new area codes could be anything. Put it all together, and now ten-digit dialing is common, and in some places required.
In places with variable-length phone numbers, how does the system know when you’re done dialing? On older phones (including most landlines, still) the system starts connecting you as soon as you enter the last digit. How does the system know that I wanted to call number 234, and wasn’t just in the process of dialing 234567?
This was how it was set up at the first three companies where I worked. At the fourth company, where I worked from 2011-2015, we didn’t have direct-dial to our extensions, so a caller would have to call the main number, and either get to a specific extension through the receptionist who answered the phone (during business hours) or through the automated phone tree (after hours).
At my current job, while I have a “work” number, it’s a VOIP number assigned to me by Microsoft Teams, and I never use it for calls to or from outside the agency; I just use my cell phone.
By coincidence, I just read a very informative technical article on this very subject a few months ago. Unfortunately, I don’t remember much about it, and I can’t even find the article any more. If I had to guess, though, I’d say the system assumes you’re done dialling once you don’t enter a new digit after a set period of time.
In my (Canadian) experience, this system is going the way of the dinosaur. I don’t remember the last time I had to call a central number followed by an extension (although it used to be very common).
The numbers would have to be set up such that this couldn’t happen. 234 couldn’t be a single number if 234567 was also a number. For instance, my area code (513) is going to be moving to mandatory 10-digit dialing later this year because we have some phone numbers that start with the 988 exchange. 988 is going to be the equivalent to 911, directing to the National Suicide Prevention Lifeline. So you’ll have to dial 513-988-XXXX to avoid mistakenly ringing up the suicide line.
Historically when you called Mabel the phone operator, you could just ask her to ring up 3226 in the same exchange and she’d cross-connect your two lines on the same switchboard. When Mabel was replaced with mechanical exchange switches, each time you dialed a number it would immediately physically connect contacts in the mechanism at the exchange. I think one way they enabled simpler 5-digit dialing was to ensure that only certain numbers could be used for exchanges and perhaps there were restrictions on the first digit(s) of the subscriber’s number such that they couldn’t overlap with other exchanges.
When I moved into my house, we started getting calls for the local CompUSA service department. They had a main phone number that ended in 0000 and would transfer people to the appropriate extension in their PBX when they called. The idiots who answered the phone did not understand that these extensions could not be reached by direct dial. They started giving people the phone number replacing 0000 with the service department phone extension, which turned out to be my home phone. Despite calls to their management I ended up getting another phone number and just dedicating the original line to my modem (I moved in a long time ago).
It wouldn’t happen; in area codes where the nuber 234 exists, longer numbers starting with 234… wouldn’t be assigned. That’s why, in my previously-mentioned small hometown, the longer numbers (longer than the old standard of four digits from my childhood) often share the same starting numbers, such as 72. Many years ago, somebody must have decided not to assign four-digit numbers starting with 72 for that area code but rather set these starting digits aside for future use with more digits.
If I had to guess, though, I’d say the system assumes you’re done dialling once you don’t enter a new digit after a set period of time.