Bulgarian communication base station installation

Until the mid-1930s, were of the "numberer" type, i.e. manually operated by telephone operators. The introduction of the first automatic telephone exchanges (ATC) in Bulgaria began with the installation of ATCs by the Siemens-Halske company, first in Stara Zagora (1935 - 600 numbers), then in Varna and Ruse (also 1935, 1000 numbers each). The first ATC in Sofia ("Levov Most" - 2000 numbers) was put into operation on June 14, 1936, followed.
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