Abstract: Cross-correlation arrangement for determining the presence or absence of a signal x.sub.2 (t) of known frequency in an unknown signal x.sub.1 (t) if this signal x.sub.2 (t) is present for at least a period of time .tau..sub.o with an unknown starting instant. An auxiliary signal a.sub.1 (t) is added to the signal x.sub.2 (t). The sum signal is converted into one-bit code words s(nT) which are multiplied in at least a first correlation channel by one-bit code words y.sub.per (kT) which are stored in a storage medium having at least N/2 addressable storage locations. The code words y.sub.per (kT) are elements of a series {y.sub.per (kT)} which is formed by the code words which occur in a predetermined time interval having a length NT and which are of a non-periodical signal of the form sign [x.sub.2 (t) + a.sub.2 (t)]. The product code words obtained are added together in an integrator. This integrator is read each time after a time interval NT and reset.

Abstract: A digital signal processing device of the recursive type, such as a recursive digital filter or a digital oscillator, comprising a storage device for storing at least one first code word related to an output code word, multiplying means for multiplying said first code word by a given weighting factor for generating a second output code word, a controlled quantizer which applies rounding or magnitude truncation upon said second code word in response to a third code word which is related to said first code word.

Abstract: Recursive digital filter comprising at least two digital delay devices, a multiplying device having two inputs which are coupled to one another in a common branch point, a summing device from which a sum signal is derived the magnitude of which is at least equal to the sum of the output signal of the multiplying device, and a feedback circuit connected between the output of the summing device and the distribution point. The feedback circuit is provided with a discarding device which acts on numbers given in sign-and-magnitude representation and which by means of magnitude truncation restricts the number of bits of the numbers applied to the branch point.