Filtering circuits, 1984, reducing the flow of words of a signal, 1984, of the type used in systems telephone a switching, 1984, filters colic products and relates to such circuits

摘要

P at the output of a converter year at high speed (1024khz) providing words of 1 to 3 e representing a speech signal has a band limited (0 - 4khz) in a central office termination equipment of the line convenience, these circuits convert the sequence of 32 incoming words in the mean values compatible with the strip convenience and which express a sample of speech by code of at least one linear 13eb with a reduced frequency has 32khz. They comprise a filter recursive passes - bottom of the second order to convert the input signal x (k): y (k) x (k) (2 - 2) y (k - 1) - (1 - 22) y (k - 2) and a filter not recursive 70 in cascade, giving the output signal (a 1024khz and 13eb): y (k) y (k) 2y (k - 1) y (k - 2) which is then read at 32khz in an output register 80. The filter 70 comprises an adder 72 and two registers 71, 74 in order to maintain two successive samples y (k), the product 2 in a simple spacing difference at the left. In the filter recursive, the spacing difference to the right (respectively 4 and 9eb) in the registers 62, 67 with retroaction of the bits coming from the division previous 64, 68 makes it possible to carry out the products by 2 and 2 without the use of multipliers, while maintaining the noise in the strip has a low level. The other three modules are of the accumulators (y, y, f). / p & & p & main application to the switching systems] convenience in by a pulse code modulation). / p