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Comment by blastofrocks | Hacker News Reader

Wait what , any number with 911 will be redirected ?

Does that for a 10 digit phone number out of 10! all possibilities, 8! are gone ?

Can there only be 3588480(10! - 8!) safe phone numbers ever ?

Nope. It’s fine to have the substring “911” in your phone number. This guy must have experienced a hiccup in the system somewhere. What I want to know is how he managed to get a secret landline installed in his parents’ house.

There was an existing RJ11 socket in the wall behind my bed. Sadly, nothing more exciting.

It's totally possible it was a hiccup. I had been using the line for weeks with the same number, and then it suddenly started to reliably redirect to emergency dispatch.

I thought I had read previously that numbers containing 911 would redirect in the case that a potential victim has misdialed in a hurry. This incident was over a decade ago, so its possible that I misread an article or found a garbage source.

Ah, you had a secret handset, not (land)line (or, as per Ernestine, instrument).

Basically, decades ago, 411 was the first "N11" to come into common use, for "local directory assistance"; and 611 was for "repair service". But all 8 were reserved ( https://www.nationalnanpa.com/number_resource_info/n11_codes... ), and there was no way they were going to rescind all the already-existing phone numbers with "11" in them, or even with "911", since they'd been in use forever.

Some random examples of real numbers with "911" in them: 800-345-1911 is the South Hackensack office of TransAxle; 800-349-1100 is (or was) Louisiana Health Monitoring.

Great examples and I had never thought to consider the origin, or even relatedness, of the N11 numbers. Thank you for the reference!

You are correct, I should have said handset. I'm not sure if this is common, but with the involvement of cellphones in the house my family began referring to any handset in the house as "the landline."

Example: "Can you grab the landline in the kitchen, I'm on the cell."

> What I want to know is how he managed to get a secret landline installed in his parents’ house.

I'm assuming the poster had a secret extension to the existing landline, not an entirely separate line.

Or they just had a spare phone they plugged into the socket their parents didn't know about (the phone not the socket). I'd be surprised if OP has gone and spliced an additional line instead of their just being a socket in their room already.

I'd be surprised if OP has gone and spliced an additional line instead of their just being a socket in their room already.

I wouldn't. This is how the nerdier of my friends got their computers online in the 80's.

In early modem days, a lot of people bought modems without thinking the whole process through. Once they got it home, they realized that either the room with the computer didn't have a phone line, the phone jack was inconveniently located, or after spending $300 on a 150-300 baud modem, they didn't realize they'd have to spend another $200 on a phone line + $50/month for the jack + $xx for dialtone.

Splicing phone lines and fishing them through the walls with a coat hangar became an art. And if it wasn't practical in your house, you sometimes ran a phone line through the trees to your buddy's house.

It was all very educational.

You're exactly correct. There was a hidden RJ11 socket behind my bed that I plugged a previously-forgotten phone into. There was only one line shared throughout the house, which occasionally caused some problems with my _master plan_.

When I was a kid I "spliced" a line (connected it to screw terminals in the box on the side of the house) from my parent's main phone to the basement so I could shotgun two dial-up modems in the middle of the night (the basement already was wired for the 2nd fax/internet line). I wasn't explicitly trying to keep it a secret, but I also didn't tell anyone, my dad found it after a couple months when he tried to make a particularly late phone call and heard modem noise.

You are correct that I did not lay an entirely separate line. There was simply just a pre-existing RJ11 socket hiding behind my bed.

Check your maths. A 10 digit number has 10^10 possibilities, but there are 8 different positions that the 911 can be in, each of which consumes 10^7 possibilities. So now there are 10^10 - 7*10^7, or 9920000000 possibilities.

(edit: Actually, this doesn't take account of multiple occurrences of 911 in the number, but it's a fairly close approximation.)

Also, at least in the US, you can't have a 1 or 0 in the leading digit, so subtract another 2e9.

This is common almost everywhere in the world as the 0 and 1 prefix (the plus in the +XXX landcodes) are usually used for international selection but might require an additional 0 or 1 after the first 0. Though in my country and most of Europe the 1 is not a international prefix.

Also no 555-XXXX numbers.

I believe I read somewhere that this is largely a myth—that some specific 555 numbers are kept empty for fictional use, but that some of them are legitimate.

Please feel free to fact check me, though.

According to Wikipedia:

Only 555-0100 through 555-0199 are now specifically reserved for fictional use; the other numbers have been reserved for actual assignment

https://en.wikipedia.org/wiki/555_(telephone_number)

While there are rules about the use of 555 numbers, there are a number of local phone companies in the U.S. that don't care, and treat it something like a 10.x.x.x IP address for local use. Things like calling the telco for repairs, or billing inquiries.

800-555-TELL used to be a voice-operated information service complete with turn by turn navigation, eventually purchased by Microsoft IIRC. XXX-555-1212 used to be an information number (both may still exist; I haven't checked).

OMG I forgot about TELLME. We used the bejesus out of that at the time.

It is entirely possible that I was wrong about numbers containing 911 redirecting. This incident was over a decade ago, and I was just recalling what I researched as a cause back when it had happened. I would be willing to bet there are people on this forum much more versed in telecom that will be able to set the record straight.

There are 10^10 ten digit phone numbers, not 10!, since you can have the same digit several times...

oops, no wonder I failed in math test at college .

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