| 摘要 |
PURPOSE:To attain the miniaturization, by providing a main trunk display lmap of a key telephone set at each push button for eliminating the need for a main trunk selecting button. CONSTITUTION:A control section 6 scans synchronizingly a button telephone set 5 at all times. When a dial push button 8 is depressed, a button information discriminating section 7 discriminates it as the selection of main trunk when a handset is hooked up before and no dial depression button 8 is depressed and discriminates it as the dial signal transmission when the handset is hooked up and the dial push button is depressed once or over. The control section 6 controls the main trunk interface 2 to operate as it is discriminated at the button information discriminating section 7. Further, when the dial push button is depressed with the handset hooked down, the discriminating section 7 discriminates it as the selection of main trunk and the control section 6 controls the main trunk interface 2 when the handset is hooked up. |
