Abstract: A method for jam-resistant transmission speech signals by radio which have been processed via vocoders, utilizing spread spectrum multiple access modulation (SSMA) or rapid frequency hopping (FH) provides, with respect to the danger of an inherent jamming brought about when a great number of stations simultaneously use the same frequency band for the same radio channel frequency group, activation and deactivation of the transmitter and receiver at the rate of the internal system frame clock pulse during a frame clock pulse period only when useful information is present. In this manner, in the case of simplexcommunication connections, on the average approximately 40% and, in the case of duplex operation, more than 60%, of the transmitting time can be saved, and hence, the inherent jamming of the system can be reduced in a corresponding fashion.

Abstract: In an installation for identification friend or foe, coded interrogations and replies of an interrogation installation of the interrogating station and of a transponder of the interrogated station are transmitted in utilizing a radiotelephony installation. The transmission of the reply (identification) proceeds according to the frequency jumping procedure via the radiotelephony installation. The interrogation of the interrogating station consists of a known encoded code word and an encoded variable data part which contains (or comprises) a frequency address. The making available (or offering) of the transmit frequencies of the transponder proceeds by means of a frequency synthesizer controlled (or operated) by the frequency address. The reply is, in certain circumstances, repeated on several, successively transmitted frequencies.

Abstract: In order to achieve a good masking, together with minimum bandwidth requirement of sample values of spectral channels which are to be transmitted in the timing of consecutive analysis intervals in a time division multiplex sum signal, and of other predetermined speech parameters which likewise represent sample values, including at least one item of synchronizing information, at the transmitting end, the time-wise overlap of the sample values and of the synchronizing information are effected pseudo-randomly within consecutive frames of the sum signal and the analog sum signal obtained in this manner is transmitted across a shaping network to the receiving end, either directly in its base frequeny, or in a desired higher frequency position, or else indirectly by modulation onto a carrier.

Abstract: In order to achieve a higher resistance to interference with respect to alien sources of deliberate interference in the use of communication connections via short waves, certain cooperative measures are proposed which include that the stations are equipped with highly-constant quartz crystal clocks and the bursts of information to be transmitted are accompanied by a time signal with the aid of which it is possible to correct any time tolerances between the stations. With an acknowledgment signal, use is made of a frequency variation of the radio frequency in the timing of consecutive burst transmissions including the acknowledgment response. The information contained in a burst in a fault safeguarded fashion is transmitted in coded form.

Abstract: A radio transmission system in which two subscribers use only one of possibly several frequency channels for a mutual connection is characterized in that in the individual frequency channel which is provided for the connection of the two subscribers the information flow of the subscriber transmitting at a particular moment in time is interrupted in, preferably, regular time intervals for a very short time in comparison with the transmission time in order to establish a return connection, in the manner of a time slot channel, having a low transmission capacity in comparison to the actual frequency channel. In this time slot channel, information of the return connection is transmitted.

Abstract: A radio system includes a fairly large number of transmitting-receiving stations which are spatially distributed over an area to be covered. Each of the stations preferably serves a fairly large number of individual subscribers in such a way that the individual subscriber can reach a subscriber who may be connected to another transmitting-receiving station. Radio frequency channels with different frequencies are provided at least for the speech channels of adjacent exchanges and positioned in a frequency range which is fixed for the system. The transmission of the individual speech channel is provided in accordance with digital methods, preferably by means of converting the signals of the individual speech channel into a PCM or a pulse delta modulation signal. Preferably, the bandwidth for the individual signal is reduced through the use of a Vocoder.