Abstract: The circuit arrangement for detecting pulse-shaped interferences in an electrical signal comprises an input (7), a high-pass filter (8) having a cut-off frequency lying between 40 Hz and 1000 Hz, one or two signal paths (25, 25') and an output (5). A signal path (25) comprises a peak detector (10), a device (11) for determining a running average value, of its input signal, a delay unit (12) and a comparator (15). The output of the peak detector (10) is coupled via the device (11) for determining a running average value to a first input (13) of the comparator and via the delay unit (12) to a second input (14) of the comparator. The comparator compares the delayed output signal of the peak detector with the output signal of the device for determining the running average value and supplies an output signal to its output (16) if the output signal of the peak detector is larger than a times the output signal of the device for determining the running average value, where it holds that a>1.

Abstract: Digital tone control arrangement for a digital audio signal, comprising a recursive digital filter whose transfer function contains as many poles as there are zeros, the recursive filter also comprising a recursive portion and a non-recursive portion each receiving filter coefficients which are stored in a memory means. So as to limit the total number of filter coefficients the memory means is divided into a first memory field for storing a first sub-group of filter coefficients and into a number of second memory fields in each of which a second subgroup of filter coefficients is stored. By means of a switching device the first subgroup of the filter coefficients is applied either to the non-recursive portion or to the recursive portion and a selected second subgroup of filter coefficients is applied to that portion (recursive and the non-recursive) to which the first subgroup of filter coefficients is not applied.