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482,267. Band - width compression. ELECTRICAL RESEARCH PRODUCTS, Inc. Dec. 1, 1937, No. 33178. Convention date, Dec. 2, 1936. Addition to 466,327. [Class 40 (iv)] In a system in which, as described in the parent Specification, signals indicative of the energy in a number of bands into which speech or other complex signal is arbitrarily divided and of the momentary value of the fundamental frequency, if any, are transmitted instead of the speech &c. itself, the transmission of these signals over a single circuit is effected with the aid of distributers instead of by carrier multiplex methods. As shown in Figs. 2 and 3, the signals, produced as in the prior system, pass to matching networks P0 .. P10 and integrating circuits 10 .. I10, which arrange for the distributer brush S to encounter on each segment a voltage representative of conditions since last the segment concerned was engaged rather than the instantaneous signal voltages existing at the moments of engagement. Additional brushes discharge the integrator circuits as soon as their record has been employed. At the receiving end, the signals are passed by distributer RD<1> to speech reconstituting circuits via filters F<1>30 ... F<1>40 arranged to prolong the effect of a signal during one rotation of the distributer but no longer. The relationship between distributer speed and signal frequency and the effect of leaving out the integrating circuits 10 &c. are discussed. In a modification, the discharging brush C is omitted and the transmission line is provided with resistances RS, R<I>S and condenser Cs as shown in Fig. 18, to cause any given signal to spread a little into the period allotted for the next. By the use of delay circuits it can be arranged that any signal comprises portions of the subsequent as well as the preceding signal, Fig. 19, (not shown). In a further modification, Fig. 20. the prolonging network in the line is omitted and the spread of one signal into the subsequent and preceding time periods may be looked after by delay networks D, 2D and attenuation pads LP arranged in 3 channels into which each channel is sub-divided. Isolating amplifiers are provided at IA. The lower part of this Figure shows a further development in which there is subdivision into seven channels to make the effect more closely analogous to that of the use of a sine-shaped scanning beam in television. The arrangement shown in this figure may have a discharging brush G similar to that shown in Fig. 2. The signals are D.C. signals and if the line cannot handle them in this form, a means may be provided to re-introduce the D.C. component at the receiving end.
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