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Office de Radiodiffusion Télévision Française
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Office de Radiodiffusion Télévision Française

The Office de Radiodiffusion-Télévision Française (ORTF) was the national agency charged, between 1964 and 1974, with providing public radio and television in France. Not it is called "Radio France".

Ever since 1945 the ORTF and its predecessors had had a monopoly in the radio and television broadcasting, although during the 1960s the public broadcaster experienced fierce competition from the "peripheral stations": French-speaking stations aimed at the French public but transmitting on long wave from neighbouring countries, such as Radio Monte Carlo from Monaco, RTL from Luxembourg, and Europe 1 from Germany (exceptionally, in 1974, RMC was allowed to set up a transmitter on French territory).

In 1974, the ORTF was split into 6 institutions:

ORTF stereo microphone system

Around the year 1960 sound engineers of the French broadcast (ORTF) found by a number of practical attempts a stereo main microphone system, which results in a quite even distribution of the phantom sources (hearing event direction) on the stereo loudpeaker base, with two small cardiod characteristic microphones, recording angle of the microphone system of +/- 48° = 96°.
This system got empirical an axle angle of α = +/- 55° = 110° and a microphone distance (microphone basis) of a = 17 cm.
Here are frequency-independent level differences effective and time of arrival differences working together in the same direction as interchannel signals (loudspeaker signals). The engineers did not want to think of a human ear distance, because an useful microphone system for a set of stereo loudspeakers should be developed. This recording technology is called mixed stereo or equivalence stereo. Usually this special microphone system must be built up from two single small diaphragm microphones. One should not use double diaphragm microphones because of the produced unbalanced directional characteristics and the larger phase responses. Even if it appears advisable to experiment with the two parameters axle angle and microphone basis to which there are practical microphone mounting devices, a firmly installed ORTF microphone set is available.