Abstract: A frequency jump radiocommunications system fixed station in which n receivers and n channels may be connected to p transmitters; p being less than n. A management circuit is provided on each of the n channels to provide signals indicating the active/nonactive state of each channel. A time/frequency law generator is provided on each channel to generate the jumped frequency signals. A general control circuit receives the active/nonactive signals and provides a connection control signal and provides a connection control signal assigning one of the n channels to one of the p transmitters. The general control circuit also generates a transmission authorization signal to authorize the p transmitters to transmit. The connection control signal is received at first and second connection matrices.

Abstract: A radio communications system comprising at least one master station and a plurality of slave stations in two-way frequency-hopping communication therewith. For telephony, speech is digitally encoded. Digital data is transmitted in packets using successive bursts at different frequencies separated by intervals of silence. Each slave station has its own frequency-hopping pattern independent of the patterns of the other slave stations but sharing a common pool of available frequencies. The master stations are capable of generating any of the slave station patterns instantly. The master stations broadcast network time information for synchronization purposes, and the slave station patterns are determined by a combination of a slave station identification number and network time.

Abstract: A radiocommunications system for transmitting packets of digitized data between a central station and a plurality of subscriber stations using a common set of frequencies. Each subscriber station and central station has an input circuit for compressing packets of digitized data, and a transmitter for generating a transmitter carrier wave. The carrier wave frequency of the transmitter is varied by steps with predetermined frequency values according to a frequency law assigned to the subscriber station and independent of the laws assigned to the other subscriber stations. The frequency steps are synchronous with the frequency steps of the other subscriber stations and the steps have the same duration. A processing circuit coupled between the input circuit and the transmitter calculates and inserts redundancy data into the succession of digitized data.

Abstract: The frequency comparator circuit serves to determine whether the signal received contains an expected signal of frequency f and time B. After clipping, the signal received is used as the logic signal A for comparison with two square-wave signals F and F.sub.q in quadrature and of frequency f. Two counters count forwards respectively when AFF.sub.q U AFF.sub.q =1 and AFF.sub.q U AFF.sub.q =1 and count backwards when AFF.sub.q u AFF.sub.q =1 and AFF.sub.q U AFF.sub.q =1. The passage of the counters through predetermined counts indicates that the expected signal has been received. In order to reduce errors and obtain a maximum count with the expected signal, a control device incorporating a delay circuit only authorises the operation of the counters when A and A delayed by K/f differ, with K such that K/f.ltoreq.B<K+1/f.

Abstract: The threshold device comprises a comparator for comparing the input signal with a threshold voltage and delivering an output signal having a first level when the level of the input signal is a white level and a second level when the level of the input signal is a black level. Storage means memorize the value of the level of the input signal when the level of the output signal of the comparator corresponds to a white level. Said storage means deliver a voltage which is representative of a fraction of the value of the stored input signal level and which constitutes the threshold voltage.

Abstract: A demodulation signal results from the sum or difference of two output signals, respectively from two demodulators applied in parallel with the signal for demodulation and in quadrature by a local carrier generator having the same frequency that the one of the received modulated signal.

Abstract: A frequency comparison circuit for determining, at least within certain limits of accuracy, whether the frequency of a received signal is equal or not to a frequency F. Generating means produce first and second reference signals at frequency F, in phase quadrature. A logic circuit periodically compares the signs m, p and q of the received signal and of the two reference signals and according to the results of these comparisons (m, p and q alike, or m different from p and q, or q different from m and p and p different from m and q) applies a pulse to the plus or minus input of a first bidirectional counter or to the plus or minus input of a second bidirectional counter, one of the two counters overflowing when the frequency of the received signal is sufficiently close to F. In a variant embodiment the second reference signal has a frequency 2F.

Abstract: The telephone set comprises a programmable carrier generator which supplies the same variable frequency to an amplitude modulator receiving the local voice signals, and to a synchronous demodulator which makes it possible to reconstitute, without band pass filtering, the voice signals of any set with which it is communicating among those of other sets. The double side band amplitude modulated signals supplied by each set are frequency-division multiplexed on one of the two ways of a telephone artery, the other way of which distributes them to the sets after conversion of all the carrier frequencies into conjugate frequencies thereof. The programmable generators of the calling and called users in communication are respectively tuned to the frequencies of such a pair of conjugate frequencies.