| 摘要 |
PURPOSE:To improve greatly the operability of a key telephone set equipped with a talk-back circuit, by providing three-kind of display states corresponding to selection modes of mode selection switches. CONSTITUTION:A talk-back circuit 1 equipped with a talk-back microphone 2 is provided with mode selection switches SW1-SW4 for switching a talk-back waiting communication mode, talk-back communication mode, and talk-back microphone-off mode. According to the selection modes of those switches SW1- SW4, a display device 4 displays three-kind of display states, so the state of the talk-back microphone is recognized easily. |
