Abstract: A peer-to-peer communication system (1) capable of operating in push-to-talk mode comprises terminals (2, 2A, 6) capable of push-to-talk, peer-to-peer radio communication, and an enhancing device (3) arranged for coupling with the terminal. The enhancing device (3) comprises: • an 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 terminal (2A; 6) is transmitting or receiving and for producing the sensor signal in response thereto, which sensor is galvanically isolated from the terminal. The communication system (1) may be a Terrestrial Trunked Radio system, commonly known as TETRA system, more in particular a TETRA system operating in Direct Mode.

Abstract: A peer-to-peer communication system (1) capable of operating in push-to-talk mode comprises terminals (2, 2A, 6) capable of push-to-talk, peer-to-peer radio communication, and an enhancing device (3) arranged for coupling with the terminal. The enhancing device (3) comprises: • an 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 terminal (2A; 6) is transmitting or receiving and for producing the sensor signal in response thereto, which sensor is galvanically isolated from the terminal. The communication system (1) may be a Terrestrial Trunked Radio system, commonly known as TETRA system, more in particular a TETRA system operating in Direct Mode.

Abstract: A method of determining ground properties comprises the steps of transmitting magnetic waves through the ground from a first location (A) to a second location (B), comparing the magnetic waves received at the second location with the magnetic waves transmitted at the first location so as to determine the attenuation of the ground, and deriving the ground properties from the attenuation thus determined. The magnetic waves are transmitted at multiple frequencies so as to determine a frequency dependency of the attenuation.