Abstract: The process consists in:using at least one transceiver station to search for a set of usable frequencies,transmitting the set of usable frequencies to the other transceivers in the networkand performing the communication transfers in frequency hopping in the set of usable frequencies communicated to all the transceivers in the network.

Abstract: In a radio communication apparatus of a specific identification number, a control part (14) produces one of first and second control signals to make a loudspeaker (19) generate an announcement in response to a received radio signal carrying an intermittent succession of frames which are preassigned to the apparatus and each of which includes first and second codewords, each comprising a call number and received with a signal condition. The first control signal is produced in accordance with the identification number, the call number of the first codeword, and the signal condition of the second codeword. The second control signal is produced in accordance with the identification number, the call number of the second codeword, and the signal condition of the first codeword. The control part may additionally produce a third control signal.

Abstract: A baseband signal communication apparatus includes a transmission unit and a reception unit. The transmission unit superposes a subcarrier on one value of a baseband signal consisting of binary values, modulates a carrier with the baseband signal on which the subcarrier is superposed, and transmits the baseband signal as a transmission signal wave. The reception unit demodulates the baseband signal having the subcarrier superposed thereon by using a demodulator upon reception of the transmission signal wave, extracts the subcarrier from the demodulated signal by using a bandpass filter, and demodulates the baseband signal by causing a detector to detect an envelope of the subcarrier.

Abstract: A transmitting and multiple line superheterodyne receiving device and transmitting device for the communications, particularly telecommunications field is disclosed. To suppress the modulation signal components otherwise generated by the transmitting device, a compensation device is provided which includes a frequency control circuit with a voltage controlled oscillator, whose nominal frequency corresponds to the sum or difference of the first and second intermediate frequencies and which is connected to a second receiving mixer.