A device for the enrichment of the modulation frequencies in the transmission of sound waves by means of the high frequency

摘要

340,060. Telefunken Ges. f³r Drahtlose Telegraphie. Oct. 31, 1928, [ConÀ vention date]. Systems for transmitting music.-In a method of improving tone colour and musical quality, e.g. in high-frequency telephony, the transmitter or receive has means for strengthening desired overtones, e.g. to compensate for previous weakening, or for inserting additional overtones. One or more fundamentals may be wholly or partly filtered out and used to provide the desired harmonics, or the sum and difference frequencies P + Q produced by modulating high-frequency currents may be influenced again by the modulating frequencies so as to produce frequencies P + 2Q, the process being repeated if desired. In the arrangement shown in Fig. 1, modulating frequencies Q in the circuit lm and high-frequency current P in the circuit V are supplied to modulating valves a1, the anode circuits of which are differentially connected. Frequencies P + Q are led to the aerial circuit and through transformers d1 to the input coil s1 of a second pair of modulating valves a2, thus producing frequencies P + 2Q. The process is repeated in the valves a3. The couplings k1, k2, k3 may be varied or omitted, so that the aerial currents may represent any desired combination of overtones. Fig. 2 shows how two melodies A, B may be simultaneously rendered ruder control of a conductor who can vary the couplings k1 - - k13 to determine the quality of each melody. The arrangement shown in Fig. 2 may be used at a receiving station, the circuits A, B being connected to different receivers, and the aerial circuit being replaced by a common distributing circuit. The overtones reinforced may correspond to those of the major triad; the intensity of the various overtones may be controlled by influencing the circuits in question inductively or capacitatively, e.g. by the hand of a conductor.