RADIO INSTALLATION

1. A radio installation having a central station to which a plurality of subscriber stations is connected by way of electric leads, at least one radio transmitting and receiving station, and a selective call device (15) which is disposed in the central station and which is switched on when it is desired to establish communication between a subscriber station and a radio transmitting and receiving station, means (35) being provided in the radio transmitting and receiving station for producing, immediately after receiving a selective call, a fixedly coded radio signal which is decoded in the central station and initiates a specific train of signals which is transmitted to the subscriber station where it is recognised as information indicating that the radio communication has been established, characterised in that the central station transmits to the calling subscriber station a first train of signals (S1) when the called radio station has transmitted to the central station a first fixedly coded train of signals (F1) as an acknowledgement of a received selective call (R) and as an indication that it is not ready to receive a call, and that the central station transmits a second train of signals (S2) to the calling subscriber station when the called radio station has transmitted to the central station a second train of signals (F2), differing from the first fixedly coded train of signals, as an acknowledgement of a received selective call and as an indication that it is ready to receive a call.