GB701011A - Improvements in or relating to electrical signal transmission systems - Google Patents

Abstract

701,011. Television. WESTERN ELECTRIC CO., Inc. June 29, 1951 [June 29, 1950], No. 15478/51. Drawings to Specification. Class 40 (3). [Also in Group XL(c)] In a signal transmission system, the value of each successive sample of the message signals to be transmitted is predicted, having regard to the individual values of a plurality of preceding samples, and the transmitted signals represent the errors in such predictions derived by subtracting the predicted samples from the message samples. At the receiver, the original message signal samples are reconstituted by a similar predictor and an adder. The predictor, which is of one of the types described in Specifications 688,099 and 701,012, may for example be a circuit for combining a plurality of preceding samples suitably weighted and of selected polarity to supply the predicted value. In the transmission of television signals the prediction is based on preceding samples in the same line, the preceding lines and preceding frames. The samples and predicted values may each be quantized before subtraction. In another arrangement, the subtractor output is quantized and feeds the predictor which is the same circuit as that used at a receiver for reconstituting the message samples. The transmitted error signals may be sent, for example, as two or three digit binary pulse code groups or error values of below a certain value may be sent as amplitude quantized pulses, greater values being sent as code groups preceded by an identifying pulse. In another arrangement the amplitudes of two error pulses may be jointly transmitted as a pulse with 16 or 25 quantization levels. If the error signal, or any digit of the code group representing the error signal, contains many successive zero values, a code group specifying the number of zeros may be sent in place thereof. Long runs of any particular amplitude may be specified by the same method, the sample amplitude as well as the length of the run being specified. Specification 679,725, [Group XL (c)], also is referred to.