Like I was a phone phreaker

picture to attract attention.

Phreaking , sometimes phreaking - fraud associated with telephone (and more recently with mobile) networks, is one of the subspecies of hacking. Source
English Wikipedia

In the distant 90s, in addition to the main work, I made a living by manufacturing and selling AONs (phones with caller ID). I lived in a small provincial town with up to 50 thousand inhabitants. He went to Moscow for spare parts for AONs to the radio market, which at that time was located in Tushino. Thanks to my passion, I had an idea about the work of telephone networks.
It all started with a note in the newspaper “Arguments and Facts” bought at the railway station for a while. In it I read a note about 2 foreigners who were caught who made international calls from a regular payphone. She sunk into my head, I began to think how this could be realized.
At that time, the overwhelming majority of payphones did not have a phone number (not determined by caller IDs) or had a phone number with category “3” (without the right to enter long-distance calls). From the payphone there was no way to call the intercity. I checked the international payphones in the city, they were all on regular telephone numbers with category “1”. The telephone number of the international payphone was written in a booth on a special nameplate.
My home telephone number belonged to the oldest telephone exchange of the three in our city, unlike other telephone exchanges in the city, it was not determined by the caller IDs, and in order to make long-distance calls, I had to dial the 8 phone number I want to call, my phone number. The PBX disconnected me, and redid it again, then connected it to the dialed number.

I want to note that in the middle of 90 about the Internet I read only in computer magazines, and in our city there was not a single provider. There was no where to get the information from; they were not published in magazines either.
I understood that the long-distance telephone exchange located in the regional center provides access to the intercity, and in order to know where to bill the phone, after dialing it issues its number in tone mode. At one of the exchanges in our city, this answer was heard. Multi-frequency tone in front of the buzzer, it was not heard on another exchange.

Together with a friend, we recorded the response of his automatic telephone exchange to a cassette recorder. I went home and after dialing 8s I tried to play it through a capacitor in a telephone line, nothing came of it. Once again I went into thought, among many thoughts and guesses, one problem arose in the discrepancy between the speeds of the tape recorders and the discrepancy between the frequencies. The next day I was already at home with a friend's tape recorder. After 8 matches and playing a tonal line, I heard the buzzer of an international station. I did not believe my success. I tried again - the buzzer. I decided to call intercity. The call went through, I talked with my friend from another city. Joy knew no bounds. I was looking forward to listing my friend for his long-distance telephone calls. It turned out to be a long-distance conversation that I made from my phone.

I understood the principle of work and I had a working prototype. Now it was necessary to create a device that generated the necessary tonality in a line. Later I found out that this device is called “Bluebox”, and it was invented by Steve Wozniak 15 years before me. And according to the Internet, they were once traded by Steve Jobs and Bill Gates. Then, due to my lack of Internet, I did not know this. And I managed to come up with everything myself.
Source

For a couple of months I created a digital device that converted the dialed number into a tonal sequence. I got the opportunity to make long-distance / international calls, substituting other numbers. First, I substituted the numbers of our local telephone numbers of machines, then the phone numbers of regional phones of machines to confuse the tracks.

Even when my phone was transferred to a digital telephone exchange, I managed to substitute another number, however, not with 100% probability.
And it all ended with the advent of the Internet, mobile phones, long-distance communication became not so expensive, maybe I began to get enough money to pay for it, or maybe it just grew.
“Bluebox” most likely is lying somewhere in the garage, if it was not thrown out, it had not caught the eye for a long time.