摘要 |
597,340. Transmission systems. PATELHOLD PATENTVERWERTUNGS- & ELEKTRO-HOLDING AKT.-GES. June 1, 1945, No. 13829. Convention date, June 1, 1944. [Class 40 (iv)] Speech is transmitted by first separating the signal into a number of partial frequency ranges, then dividing the frequency of each of these ranges, combining these results to form a signal for transmission, separating out the components at the receiving end, multiplying their frequency separately to form the original components, and then combining them to form the original speech. Auxiliary signals may be mixed with the components before transmission and these signals then have to be removed at the receiving end. The frequencies for transmission can thus be adjusted to obtain a narrower wave band. Apparatus for carrying out this method of transmission may also be combined with means for scrambling the speech. In one method of carrying out the invention, shown in Fig. 5, each frequency range is separated by a band-pass filter BP, the amplitude is limited in AB and the frequency divided in TE. The resulting signal is fed to a modulator M controlled by a voltage proportional to the amplitude of the original signal and produced by a rectifier G and a low-pass filter TP. The resulting signal therefore has the amplitude of the original signal, but a fraction of its frequency. In the receiving apparatus shown in Fig. 6, the bands are reproduced by filters BP and a signal of constant amplitude but multiplied to the original frequency is produced by the limiter AB and multiplier VE. The modulation product of this and the signal from BP pass through a high-pass filter HP and the original partial band signal is produced. The signals indicating amplitude and frequency may be transmitted separately instead of combined as above. |