| 摘要 |
PURPOSE:To enable to audio call out during communication without increasing lines, by providing the call out control signal part, in the key telophone set using three pairs of lines. CONSTITUTION:When incoming signal is given from the main line 2, the incoming is detected at the main line circuit 4, and when tone call is made to the key telephone set 21 preset, call out tone is produced from the main line call out circuit 9, and it is fed to the call out speaker 17 via the point 8a of the call out cross point 8, terminal circuit 11B and call out audio delivery line 28, and the call out tone is produced from the speaker 17. In this audio call out, the call out cross point 8 is provided independently of the communication cross point 5, and since the call out tone is delivered with separate path from the communication path, call out is enabled even if the key telephone set 21 called is in communication. |
