A transmission system for the transmission of binary synchronous pulse signals in the base group of a carrier telephony system in which these pulse signals are converted into two separate pulse signals, at half the original information speed each, which separate pulse signals are each modulated in accordance with a single sideband method on carrier signals of different frequencies located on either side of the central portion of the transmission band (base group) so that the transmitted frequency spectrum is constituted by the two non-adjacent single sideband signals.The invention relates to a transmission system and associated transmitters end receivers for the transmission of binary pulse signals in a prescribed transmission band within which the pulses coincide with the pulses of a clock signal having a given clock frequency, said pulse signals being modulated on a carrier signal in a modulator at the transmitter end and at the receiver end being demodulated in a demodulator the output signal of which is applied to a pulse regenerator, while pilot signals are co-transmitted with the pulse signals modulated on the carrier signal, which pilot signals are selected at the receiver end in a pilot circuit so as to generate a local carrier and clock signal.In order to be able to take an unambiguous decision regarding the presence or absence of a pulse in the transmitted pulse signal at the receiver end in such transmission systems, special attention must be given to the delay time characteristic of the transmission path. Particularly the requirements to be imposed on the delay time characteristic become more stringent when the information speed is very high. In fact, a high information speed necessarily results in a reduction of the pulse duration of the pulses to be transmitted so that frequency components of higher frequencies are introduced which are greatly influenced by the delay time differences in the transmission path.When transmitting pulse signals having a high information speed in the base group of a carrier telephony system having a bandwidth of 48 kHz serious difficulties are experienced; in fact, it has been found that the delay time characteristic turned out to be very unfavorable for the high information speed of, for example, 48 kilobits/sec. Not only is the delay time characteristic of carrier telephony systems degraded by the use of bandpass filters and pilot cut-off filters, but also by the group switching filters conventionally used in international communications, which filters have a very poor delay time characteristic. Thus, in the base band of a carrier telephony communication delay time differences of 100 .mu.sec were measured which are even considerably larger than the duration of the pulses of 21 .mu.sec to be transmitted.An object of the present invention is to provide a transmission system of the kind described in the preamble is suitable for pulse transmission in the base group of a carrier telephony system and which with its flexibility in use and its simplicity in structure is distinguished by a minimum sensitivity to the delay time characteristic of the transmission path. Thus, it was found that for the transmission of pulse signals at an information speed of 48 kilobits/sec, it was not necessary to use delay time equalizing networks, while even in case of a 100 percent increase of the information speed a very light delay time equalization due to the use of a seven-level coding was already found to be amply sufficient to guarantee optimum receiving conditions.The transmission system according to the invention is characterized in that the modulator is constituted by a dual single sideband modulator consisting of two parallel-arranged channels binary pulse signals being applied to said channels each channel including a coder for converting the applied binary pulse signals into multilevel pulse signals, while a lowpass filter and a single sideband modulator are connected in cascade to the output of each coder, said single sideband modulators being controlled by mutually different carrier signals having frequencies located on either side of the center of the transmission band, the outputs of said single sideband modulators being applied to a combination device to produce a dual single sideband signal constituted by the two single sideband signals at the outputs of the single sideband modulators and having a frequency space left around the center of the transmission band for the transmission of two pilot signals, the ratio of the clock frequency and the frequency difference of the two pilot signals being given by an integer, the demodulator in the receiver being constituted by a dual single sideband demodulator comprising two single sideband demodulators the received dual single sideband signal being applied to each of said demodulators, each single side-band demodulator being controlled by a local carrier signal said carrier signals having mutually different frequencies, the output of each single sideband demodulator being connected to a decoder controlled by a local clock signal which together with the two local carrier signals is derived in the pilot circuit from the received pilot signals.Simultaneously, with the minimum sensitivity to the delay time characteristic of the transmission path at the high information speed of 48 kilobits/sec of the pulse transmission in the base group of a carrier telephony system, the use of the steps according to the invention also results in a considerable frequency division of the frequency band of the base group. For example, this frequency division creates the possibility of an undisturbed transmission of all internationally standardized pilot signals in the base group of a carrier telephony system, particularly the pilot signals of approximately 84, 104 and 64 kHz and four speech channels each having a bandwidth of 4 kHz can be incorporated in the base group. As a result an optimum utilization of the available frequency band is obtained while it is found that the different signals in the base group are not influenced.