| 摘要 |
The system requires a telephone PABX system and makes use of specific user facilities of the PABX system. The door telephone stations (TT) are designed as telephone subscriber stations and are connected to a telephone PABX system in which a connection can be set up simultaneously or alternately between a subscriber station and at least two further subscriber terminals. The door-closing devices (SK) assigned to door telephone stations (TT) can be activated via their own subscriber terminals (TK) of this PABX system. A door-closing device (SK) which is to be actuated is in each case activated by an answering station (TN), which is connected to a door telephone station (TT), by means of an enquiry call, broker's call or conference connection. A door telephone and door-opening system implemented in this way is particularly advantageous when door telephone stations (TT) which are relatively far apart from one another and door-closing devices (SK) are to be operated, since the installation cost required for this purpose can be kept within acceptable limits. <IMAGE>
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