Abstract: To facilitate the supervision of directly dialed long-distance telephone traffic, output signals from call monitors (G.sub.1 -G.sub.n) associated with a number of trunk lines are fed to a plurality of multisensor signal detectors (SD) of an associated exchange working into a data-input unit (ID) which includes a serializer (MS) assembling signal samples from all the sensors into a comprehensive frame. The frame serializer comprises a number of multiplexers (M1-M16) which, in the course of a scanning cycle consisting of 16 subcycles, feed respective output frames from the several detectors during each subcycle to corresponding cells of a shift register (SR). Each output frame contains bits from an associated set of sensors that are sequentially read out during the subcycle in which they are loaded into the shift register. If a given set of sensors is to be scanned at the maximum rate, i.e. 16 times per cycle in this instance, the corresponding multiplexer is not switched between subcycles; otherwise, i.e.

Abstract: To facilitate the supervision of long-distance telephone traffic over an extended area, output signals from call monitors associated with a number of trunk lines are fed to respective detectors working into a common preprocessor in which certain parameters of toll calls carried by each of these trunk lines, such as number and length of engagements, number and length of conversations and number of metering pulses, are registered in real time with the aid of respective counters for subsequent transfer to a final processor. The contents of each counter are read out to a buffer memory, within the preprocessor, upon the termination of the respective call or at any time in response to an external command. The preprocessor may be duplicated in order to minimize the effect of malfunctions, with inhibition of the loading and unloading of the counters of either unit until a confirmation signal is received from the other unit or a certain number of operating cycles have elapsed.