As the development of urban and intercity telephone networks increased, the need was increasingly resognized to replace the manual telephone exchange service with automatic telephone exchanges (PBX).
The start of intensive development and automation of our urban telephone communication system began in 1929, when in Rostov-on-Don, the launch of the first ATS 6000-room machine took place.
Zamoskvoretskaya of ATS 8000-room and Bauman PBX 7000-room machines were commissioned in Moscow in 1930.
Construction of these stations was by the Red Dawn Leningrad plant. Technical and technological documentation was prepared by the Swedish firm L.M. Ericsson, who also participated in the project design and construction.
At the same time there were operating PaBXs in Novosibirsk, Tashkent, Smolensk, Leningrad and other cities. The PaBX machine was produced in the USSR until 1941. During the Great Patriotic War work on automation of Russia'a telephone networks was suspended