I wrote a "ring knocking" tool back in my college days so that I could connect to my Linux box at home from the labs at school since I was on dial-up. I'd go to the payphone, put in a quarter, call my line and let it ring the requisite number of times, hang up, get my quarter back, then go to the lab and check my school email account. The ringconnectd daemon would detect the rings, wait a few seconds, connect to my ISP, and mail me its current IP address.
I tried to do something similar not too long ago. Different application really, but I wanted to do something on the other end depending on how often it rang. Sadly I discovered that apparently in all-digital "modern" phone networks (SIP, VoIP etc.) the ringing tone you hear as a caller is simply ingested by your network operator and the tone you hear as the one getting called is basically just some audio file that plays over and over, triggered by a single "hey, someone is calling now!"-message sent by a modem unit, which to my surprise are still using AT commands to this day. Bummer. Turns out even the duration of how long it rings depends on too many factors, so what you hear on one end (ringing) might be off by multiple seconds on the other end.
At least it explains the "You only heard it ring once? I let it ring like five times before I hung up! Seriously!"-anecdotes I keep picking up. :)
> the ringing tone you hear as a caller is simply ingested by your network operator
In my experience this depends on the network in question: SIP supports "early media" and I've seen it in action a few times. You can tell by the fact that phone UIs usually don't count connection time in that state, yet you can hear a prerecorded announcement, music mixed with the dialing tone etc.
I remember some creative uses of this as well: If you controlled the signalling stack, it was possible to keep a connection open in this state indefinitely without either end getting charged.
This is also true with silences. When we switched from analogue phone calls to digital phone calls in the 90's, SIP began to ingest white noise during silences due to discomfort perceived by the users thinking they got hung up or the network has been disconnected.
When I was a teenager in the 90s in the UK, if I wanted my parents to collect me from somewhere then I could let them know by calling the operator from a payphone and asking for a reverse charge to my parents landline. Calls to the operator were free but reverse charged calls cost a lot to those who accepted them.
When asked for my name I would usually use my first name and use my last name as the place to pick me up from. If that gave them enough information then they could reject the call, which would cost them nothing.
When I went to sleep away camp one summer when I was 11, it required me to take an airplane by myself. To let my parents know I had arrived, they told me to call collect, use my regular name, and they would reject the call.
If it was an actual emergency, I was to immediately call back again and then they would accept the call. It was a great way to get free messages.
Ah, memories! Later in the 90s they (who?) introduced a new automated service which I think was called “0800 REVERSE”. The beauty of it being automated was you could quickly give the required message in full, or even the number of the payphone you were calling from.
Yep, one of my friends in high school (1980s) was on my sports team. He would call his mom "collect" from the school's payphone [0] at the end of each practice (end times varied by as much as an hour) and the name was something from a Chevy Chase movie (Fletch?) and his mom would reject the call, and get in the car and head over to pick him up.
[0] Remember this was the 80s, no mobile phones. And a collect call was free from a payphone, since the callee was expected to accept and pay the charges.
Some memories with those time. We used missed calls for varying reasons depending on the people we interact with.
* When going to meet someone, first missed calls says you've started, then the second missed calls says you've reached. This will be informed before hand while scheduling the meet.
* You're supposed to reject when you're expecting a mutually agreed missed call, and if the call comes the 2nd time immediately, then you should pick up.
* During meets, there usually is one organizer who everyone gives missed call to update their status and they'll follow-up with another missed call to those who didn't update. I know it sounds complicated, but it surprisingly isn't.
* Before mobile, landline was pretty common and caller IDs were almost non-existent, missed calls with a pattern are the way to denote that its you that's calling to make sure her parents does not pick up the phone :). One ring, then two rings, and she should be near the phone for the next call to pick (you hope and pray its not her dad, again.) and pretend to talk with a friend.
Yup, there were several tricks like these!
My father used to travel a lot and paying for roaming was expensive. So when he was available to speak, he'd just give a missed call at a fixed time and we used to call him from the landline (much cheaper). If we didn't get a missed call, he was busy.
I also remember while going to college, I had bus connectivity, but had to walk the last 3km or so home. I used to call either of my parents to come pick me up when I was around 15 minutes away from the bus stop.
Long before cell phones and answering machines my Dad was a pharmacist in a small town. He was happy to drive down to the drugstore when a customer called our home needing an after-hours refill, except on Sunday which was his recharge day. On Sundays we were instructed never to answer the phone unless it rang twice, paused, then rang again. Close family members knew the secret code; customers just learned Dad wasn't available on Sundays.
My (now retired) pharmacist said he got a call on Christmas Day because someone got someone a surprise travel holiday that left the next day and they didn’t have enough meds to be away that long.
He doesn’t believe they realized he was half in the bag filling their prescriptions.
Same here. Even if my dad wasn't on call, his job would call every saturday and sunday with some dumb emergency caused by their own cheapness. So we pulled the phone plug at night, and at daytime we counted the rings.
Eastern Europe already checked in, but I thought I'd add yet another anecdote.
In St Petersburg, Russia the only GSM provider had luxurious free 10 seconds, and $0.40/minute after that. Plus fixed monthly fee, of course. $0.40 was very expensive by Russia late 90s standards and at that time mobile phones were used by three (or really just two) distincitve groups: gangsters, emerging business people, and... dudes in IT.
Criminals didn't care about money, but IT crowd was crafty and resourceful.
Some phones allowed to configure a beep after 9 seconds prompting you to hang up and redial. Those were valued, but it didn't stop at that - there was even a cottage industry of firmware and hardware hacks for certain models to drop the call and redial automatically.
...and then providers switched to only 5 and then 3 seconds, and $0.10/min, yet for a few more years there were still annoying die-hards who kept their modded phones and old contracts with free 10 seconds and ridiculous price, which were no longer available for new clients.
I used Google calendar to send free SMS to myself with information about my services running on my raspberry pi. Each service had a future calendar entry with SMS reminder. Under normal operation the service would move the entry forward in time. If it had crashed, I got a SMS.
We also had an understanding of the number of based on the number of rings, too: 1 ring and hang up was when my aunt got home and 2 rings was my cousin got home. They could call us long distance to let us know they got home OK.
Yeah this was big among my age group in Australia too, in the late 80s early 90s. Pay phones only charged if the other end picked up, so it was an easy way to tell dad to pick you up or that you’d be late.
Pay phones (the yellow ones) in Melbourne in the early 90s let you both hear each other for under 1 second. Calling multiple times you could let your parents know to pick you up from wherever you were :)
When I was young I used to use the 1800-REVERSE number, which would require the person answering the phone to pay. I thought it was a great way to contact my parents if I had run out of phone credit.
This was a thing among my parent's friends and relatives when I was a child in the north of England in the seventies. People would say something like "give me two rings to let me know you got home safe". I have no idea what the cost of landline calls was back then.
It also features in Iain Bank's novel Whit from 1995. The main character is a member of a Scottish religious cult, who mitigate their exposure to "ungodly" technology by using a message-passing code based on the number of rings before hanging up. Its a long time since I read the book, but I seem to recall some detail about it having to be error-tolerant because the ring-tones that the caller hears don't necessarily match those heard by the recipient.
Readit News
It was my second open source project: https://www.ibiblio.org/pub/Linux/system/network/daemons/rin...
I was still getting support requests for it in the late 2000s from people who were using it in South Africa :)
At least it explains the "You only heard it ring once? I let it ring like five times before I hung up! Seriously!"-anecdotes I keep picking up. :)
In my experience this depends on the network in question: SIP supports "early media" and I've seen it in action a few times. You can tell by the fact that phone UIs usually don't count connection time in that state, yet you can hear a prerecorded announcement, music mixed with the dialing tone etc.
I remember some creative uses of this as well: If you controlled the signalling stack, it was possible to keep a connection open in this state indefinitely without either end getting charged.
Here's a relevant RFC: https://tools.ietf.org/html/rfc3960
That's an amusing typo - I suppose that should be 'injected', but Pac-Man pops to mind ...
When asked for my name I would usually use my first name and use my last name as the place to pick me up from. If that gave them enough information then they could reject the call, which would cost them nothing.
If it was an actual emergency, I was to immediately call back again and then they would accept the call. It was a great way to get free messages.
https://en.wikipedia.org/wiki/Von
[0] Remember this was the 80s, no mobile phones. And a collect call was free from a payphone, since the callee was expected to accept and pay the charges.
* When going to meet someone, first missed calls says you've started, then the second missed calls says you've reached. This will be informed before hand while scheduling the meet.
* You're supposed to reject when you're expecting a mutually agreed missed call, and if the call comes the 2nd time immediately, then you should pick up.
* During meets, there usually is one organizer who everyone gives missed call to update their status and they'll follow-up with another missed call to those who didn't update. I know it sounds complicated, but it surprisingly isn't.
* Before mobile, landline was pretty common and caller IDs were almost non-existent, missed calls with a pattern are the way to denote that its you that's calling to make sure her parents does not pick up the phone :). One ring, then two rings, and she should be near the phone for the next call to pick (you hope and pray its not her dad, again.) and pretend to talk with a friend.
I also remember while going to college, I had bus connectivity, but had to walk the last 3km or so home. I used to call either of my parents to come pick me up when I was around 15 minutes away from the bus stop.
He doesn’t believe they realized he was half in the bag filling their prescriptions.
In St Petersburg, Russia the only GSM provider had luxurious free 10 seconds, and $0.40/minute after that. Plus fixed monthly fee, of course. $0.40 was very expensive by Russia late 90s standards and at that time mobile phones were used by three (or really just two) distincitve groups: gangsters, emerging business people, and... dudes in IT.
Criminals didn't care about money, but IT crowd was crafty and resourceful. Some phones allowed to configure a beep after 9 seconds prompting you to hang up and redial. Those were valued, but it didn't stop at that - there was even a cottage industry of firmware and hardware hacks for certain models to drop the call and redial automatically.
...and then providers switched to only 5 and then 3 seconds, and $0.10/min, yet for a few more years there were still annoying die-hards who kept their modded phones and old contracts with free 10 seconds and ridiculous price, which were no longer available for new clients.
We also had an understanding of the number of based on the number of rings, too: 1 ring and hang up was when my aunt got home and 2 rings was my cousin got home. They could call us long distance to let us know they got home OK.
Another trick was to place operator-assisted person-to-person calls with the names of different fictional people representing different messages.
For example, Harvey Jones could mean "Pick me up at the diner."
It also features in Iain Bank's novel Whit from 1995. The main character is a member of a Scottish religious cult, who mitigate their exposure to "ungodly" technology by using a message-passing code based on the number of rings before hanging up. Its a long time since I read the book, but I seem to recall some detail about it having to be error-tolerant because the ring-tones that the caller hears don't necessarily match those heard by the recipient.