In the late 1960s, in the Moscow City telephone Network, the largest in the country, a reform of telephone numbering was planed. This was a very important event in the history of telephony.
The reform centered on the abolition of the letters in phone numbers (up to this point, all telehone numbers began with letters) and the transition to a seven-digit numbering system.
In subsequent years, such transitions were carried out (and implemented) in a number of other populous cities of our country.
The introduction seven-digit telephone numbers enabled signalers to systematically expand the telephone network.
A complete phone number in Russia has 10 digits: the first three are the area code. Then comes the locality code (except for a few large cities with seven-digit numbers) and finally the actual landline number.
A full long distance number can have up to 15 digits, in addition to containing a local number code of cities, countries and networks.