| 摘要 |
A push-to-talk communication system (1) comprises user units (2) arranged for radio communication, one user unit (2A) being designated as main user unit. The system further comprising a device (3) for enhancing communication, which device is arranged for use with the main user unit and comprises:
€¢ a directional antenna (31) for transmitting and receiving radio signals,
€¢ a band-pass filter (32) for selecting a frequency band of the radio signals,
€¢ a bidirectional amplifier (33) for amplifying radio signals alternatingly in a transmitting and in a receiving direction,
€¢ a control unit (34) for controlling the bidirectional amplifier (32) in response to a sensor signal, and
€¢ a sensor (35) for detecting whether the user unit (2A) is transmitting or receiving and for producing the sensor signal in response thereto, which sensor is galvanically isolated from the user unit. The communication system (1) may be a Terrestrial Trunked Radio system, commonly known as TETRA system, more in particular a Direct Mode Operations TETRA system.
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