| abstract |
A Private Branch Exchange (PBX) is described comprising a control section 11-2, a digital key telephone interface 14 connected to a digital key telephone 2, a station line interface 16 connected to station lines 20 and a leased line interface 36 connected to leased lines 30. When the user wants to establish an emergency call they are required to un-hook the digital key telephone 2, or operate the extension key, the station line key or the leased line key and dial the appropriate emergency number eg.911. Consequently, the control section 31 releases any currently captured line in favour of a dedicated emergency line, the number of which is stored in line number memory section 32. The dialling data is then read from dial memory section 29 and is transmitted to the MF tone creation and transmitting section 17-2. The dialling data is converted into a MF tone signal which is output on the emergency line. |