Abstract: A system for recording and/or reading an information signal (V.sub.i) on an elongated track (4) of an optically readable record carrier (1). A position-identifying signal (V.sub.p) which is synchronous with a clock signal is recorded on the track 4 by modulating the transverse excursion of the track, the signal V.sub.p indicating the instantaneous position along the track at which the information signal V.sub.i is located. The frequency band of the position-identifying signal V.sub.p is situated substantially outside the frequency band of the information signal V.sub.i. In manufacturing such a record carrier, the deflection of a recording beam of radiation in a direction substantially transverse to the track is modulated by the position-information signal V.sub.p.

Abstract: A manually operated or automatic equalizer (1) with adjustable band filters for varying the frequency characteristic of an electric signal presented to an input (2) and for applying a frequency characteristic-adapted electric signal to an output (3). The equalizer has a plurality of band filters (F.sub.1 to Fn) with their bands located adjacent to one another in a given frequency range. The distance (frequency separation) between the central frequencies of filters having neighboring bands is greater than the distance between the central frequencies of one third octave filters having neighboring bands located at at least approximately the same frequencies as those of the band filters (F.sub.i). At least those band filters (F.sub.1 to F.sub.m) whose bands are located in the low-frequency part (f<450 Hz) of the frequency range have a central frequency (fc.sub.i) which is variable. A digital filter which can be used as a band filter in the equalizer is also described.

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.