| 摘要 |
PURPOSE:To save the number of times of calling of the user by supervising the transition of hook state of an extension telephone set, allowing an extension telephone set at the caller side to estimate whether it copes with an incoming call or not and generating a preset call at a proper time. CONSTITUTION:When a caller dials a number of an extension telephone set 1n of a called party by using an extension telephone set 11, the number of the extension telephone set 11 is written in a storate section 6 and the number of the extension telephone set 1n is written in a storage section 8. A central operation processing unit 5 supervises the hook state of the telephone set 1n by using a storage section 7 and when the set is in hook-on state, a signal source 4 is controlled to generate a call signal and the telephone set 1n is called via a switching circuit 3 and an input/output device 2n. When the hook-off state of the telephone set 1n is detected, the number data of storage sections 6, 8 is read under the control of the central operation processing unit 5, the input/output device 3a operates the switching circuit 3 to acquire a channel connecting the telephone sets 11 and 1n. |
