Abstract: Binary digits of one kind are each converted into a single, complete sinusoidal oscillation of a lower frequency, and binary digits of the other kind are each converted into a train consisting of an oscillation packet of a higher frequency and a single, complete sinusoidal oscillation of the lower frequency. At the receiving end, only a comparator as limiter, a low-pass filter, and a threshold-value detector are necessary to produce from the transmitted signal a train of pulses of equal length separated by spaces of different lengths. From this pulse train, the binary digits can easily be derived. Because of the simplicity of the equipment at the receiving end, the system is particularly suitable for transmitting data from one transmitter to a large number of receivers.

Abstract: A selective calling arrangement for use in a radio communications system or the like. Each of the receivers in the system is assigned an unique binary code number which is transmitted to the receivers by r.f. pulses of fixed width separated by one of two fixed intervals respectively representing a binary "1" or a binary "0", the selective calling system being unaffected by the chopping of pulses on the transmission path.