Importance

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Abstract

Entrance telephone installation intended to be connected to a public telephone network, said installation including a number discriminator with line access and dialling facilities, addressable from an entrance telephone set for connection of a circuit to specific reply sets, said reply sets being arranged to facilitate signalling via the circuit switched through in the telephone network to accomplish door lock opening. According to the invention, a specific ID-signal is transmitted to the telephone network during a first predetermined time period after completed switching operation to a specific reply set, with simultaneous monitoring of the telephone network with regard to digits entered from called reply set transferred via the telephone network as a pulsed signal, multi frequency signal or optical signal, absence of such digit entered from the reply set during said first time period resulting in disconnection of the connection. Detection of one or a number of digits entered from the reply set during said first time period being interpretated as specific commands, which are transformed into specific actions, for example establishment of video and/or speech communication with the entrance set, blocking action preventing repeated calls during a predetermined time period, immediate disconnection, alarm transmission from the entrance set or any other predetermined function. The first time period is followed by a second time period, provided that a predetermined digit is entered during the first time period, whereunder video and/or speech communication can take place between the reply set and the entrance set. Digits entered from the reply set during said second time period are detected and interpretated as specific commands, which with regard to resulting function for one or a number of individual signals result in different resulting functions in relation to corresponding signal(s) during the first time period.

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First Claim