Company Microphona (when the international transcription -like usual at this time - was used) was founded by brothers Knotek (Antonin and Ludvik) in 1920, first in two rooms on Jirecka ul. Praha VII, as service for telephone microphones and signaling devices. Thanks to orders by Ministry of Post and Telegraphy the company grew up to eight rooms and started to produce of private telephone devices. In year 1925 company acquired from Dr. Brandt patent for production of automatic telephone switchboards. The existing rooms were not enough for bigger production (80 employees about) and company moved to Hermanova ul., later in 1927 to Husova ul. The portfolio was enlarged to big automatic switchboards, signaling, alarming, hospital, hotel and more other devices. Caused by big boom on the market, company established in 1930 new facility in Flora, Praha. Caused by fire on end of December the facility in Husova ul. was not usable more. Company bought and renewed building in Strasnice, where the production had started on spring 1931. The company was increased in 1933, the total staff counted 430 people. Under pressure of economical crisis company started production in new market segment - radio receivers. It was a good decision and the company staff grew up again up to 680 people. The international political situation has got very complicated and to show the owners patriotism, the company logo was changed to Czech transcription - Mikrofona. It helped them a lot of on the CS market. Through that, after Nazi occupation the radio production was cancelled in 1940. After WW2 the civil production was recovered, but in December 1945 the company was nationalized and in 1946 included to newly established Tesla.