| 摘要 |
PURPOSE:To attain freely calling to a trunk line from a called telephone set even if a call button is operated during on-hook by connecting the called telephone set to an extension circuit with the re-operation of a call button after the off- hook of a calling telephone set. CONSTITUTION:When the calling button CKa of a telephone set STa being a calling telephone set is turned on while keeping on-hook, it is detected by a call detecting section CAD, a control section CT is responded by the detected output and the telephone set STa is connected to the extension circuit. Then, in hooking off the telephone set, it is detected by an off-hook detecting section OHD and when the calling button CKa is turned on again after the detection, it is detected by the call detecting section CAD, the control section CT connects a telephone set STb to the extension circuit based on the detected output of the detection sections OHD and CAD and an extension call tone is transmitted to the called telephone set STb by a call tone transmission section CTS. When the telephone set STb hooks off in response to the transmission, the extension talking circuit is completed. |
