| 摘要 |
<p>KEY TELEPHONE AREA VOICE PAGING CIRCUIT AND METHOD An area voice paging feature is provided in a key telephone system wherein key telephone station sets each have a loudspeaker circuit responsive to a d.c. control signal, on an associated signalling path, to audibly reproduce voice band signals superimposed on the d.c. control signal. A page control interface circuit generates a page control signal in response to receiving the d.c. control signal, when the d.c. control signal is directed to the interface circuit on one of the signalling paths, and generates a d.c. biased voltage signal having an a.c. component corresponding to the voice band signals. Page switches each have an output connected in common with a predetermined respective one of the signalling paths and are each responsive to the page control signal to couple the d.c. biased voltage signal to the respective signalling path. Each loudspeaker circuit, in a group as selected by the page switches, receives the d.c. biased voltage signal and produces an audible signal corresponding to the a.c. component. In the case where one of the signalling paths is already in use, this is indicated by the presence of the d.c. control signal on the signalling path. In this event, a logic circuit in the page switch senses the prior presence of the d.c. control signal and the d.c. biased voltage signal is prevented from being coupled to the already occupied signalling path.</p> |
