Abstract: A method for signalling/communication within an entrance telephone system or similar, and a system utilizing the method, which facilitates selective communication from an entrance center or central unit (1) to a desired and addressed substation (5, 5', 5") via a loop including at least two conductors, and which also facilitates entrance lock opening or a similar function from such a substation (5, 5', 5"). After approved addressing operation of the central unit (1) is performed by a visitor, the central unit (1) feeds work current to the loop (2, 2') joining the central unit (1) and connected substations (5, 5', 5"). By using a signal detecting means (6, 6', 6") only the addressed substation (5, 5', 5") then establishes a galvanical connection with the loop (2, 2') and the central unit (1).

Abstract: An entrance communication system including a programmable number discriminator, arranged to perform an automatic dial-up operation via the public subscriber telephone network to selected subscriber telephone set when addressed from an entrance set, and to establish voice communication therebetween, preferably also accepting control instructions sent as digits from the called party. At least one local communication circuit is included for direct communication between the entrance set and at least one dedicated reply set, which is not connected to the public subscriber telephone network. At least one dedicated reply set is preferably arranged connected to gain access to the line access and dial-up function for establishment of alarm calls or other telephone calls via the public subscriber telephone network.

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.

Abstract: A method and apparatus for transmission of alarm signals by utilization of an entrance telephone set system connected to a public telephone network, of the type including a selectively addressable telephone number dialing device, preferably of the type disclosed in U.S. Pat. No. 3,947,641, the telephone number dialing device being connected to one or a number of manually or automatically operable alarm indicators, which when operated initiate dialing of predetermined telephone numbers.