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1. WO1984000455 - EQUIPEMENT DE TRANSMISSION TELEPHONIQUE SANS FIL

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[ EN ]
CLAIMS

1 Equipment for wireless transmission of telephone calls, in which there is included a plurality of pairs of coacting units (1, 3) between which telephone calls are to be transmitted, each pair comprising a stationary unit (1) connected to a telephone line (2) and provided with a radio transmitter (11) and a radio receiver (12), the other one of the pair being a telephone handset (3) at a distance from the stationary unit, provided with a radio transmitter (24) and a radio receiver (25), both units each being provided with an array of monitoring circuits (17, 30) and a channel selector (15, 28) for selecting a usable radio speech channel amongst a plurality of such channels common to all pairs of units (1, 3), where
the radio speech channel is a single, selected dedicated frequency band for duplex speech between the units (1, 3) in the pair, and
time-controlled send-receive switches (41, 51) in each of the units are adapted for mutual coaetion in a pair of the units for changing transmission direction at short time intervals, and
the radio transmitters (11, 24) are adapted with time compression means (42, 52) for sending speech signals with higher than real time speed, and
the radio receivers (12, 15) are adapted with time expansion means (43, 53) intended to give back the real time speed to the speech signals,
characterized in that each send-receive switch (41, 51) is adapted to distribute send and receive time intervals with a total length for transmission and reception which is constant; and in that the time compression means (42, 52) of each radio transmitter (11, 24) has an adjustable degree of compression, this means being adapted for coaetion with the send-receive switch so that when a speech signal is lacking in a transmitter, said means assigns the major portion of its transmission time to the other transmitter of the coacting units, the degree of time compression of this latter unit being caused to change so that the assigned transmission time will be filled by its speech signal.

2 Equipment according to claim 1, characterized in that the radio transmitters (11, 24) for the speech signals are each adapted with an analogue-to-digital converter connected to the time compression means (42, 52), which is provided with digital - circuits, and a digital-to-analogue converter connected to said time compression means before the radio transmitter, in that the radio receivers (12, 25) are each adapted with an analogue-to-digital converter, coupled between the receiver demodulator and the time expansion means (53), which is provided with digital circuits, and a digital-to-analogue converter connected to said time expansion means before the receiver earphone circuits.

3 Equipment as claimed in claim 1, characterized in that the radio receivers (12, 25) are adapted for operation according to the homodyne principle, and that the carrier frequency of each radio transmitter (11, 24) is equal to the frequency of the local oscillator of the radio receiver incorporated in the same unit (1, 3).