frequency sweeps which a second reference oscillator generates in the second receiver channel is shown in fig2 a 2 e a method which is a variant of the one in fig1 a 1 c where four different symbols can be transmitted point to point on a channel is shown the information is in this case contained both in start frequency and sweep direction the following four sweeps are possible wherefore the capacity of the transmission is 2000000 baud or 4 mbit s the four sweeps represent the value of a symbol which for example consists of two binary bits each being a logical one or logical zero a 00 positive sweep from centre frequency f 0 u2192 f 0 100 mhz b 01 negative sweep from centre frequency f 0 u2192 f 0 u2212 100 mhz c 10 positive sweep towards centre frequency f 0 u2212 100 mhz d 11 negative sweep towards centre frequency f 0 100 mhz u2192 f 0 a transmitted sequence modulated according to this method is illustrated in fig2 a which shows the transmitted frequency as a function of time in demodulation four receiver channels are used in the receiver which each is used for verifying the presence of a certain sweep see fig2 b 2 e which show the oscillator frequencies as a function of time for the four different receiver channels the method described above can also be used for providing transmission intended for transmission on two independent channels in the same frequency band which is illustrated by the diagrams in fig3 a 3 e by using this method.