| 摘要 |
PURPOSE:To simplify the whole constitution remeakably by utilizing S bits of an envelope signal for origination, call detection display, selection, call display, answer, busy display, etc. CONSTITUTION:At a telephone set 2 side, an envelope signal EI obtained by setting S bits of an envelope signal E to ''1'' is obtained through calling operation and sent to a switchboard 1 side. At a switchboard 1, it is detected to obtain the envelope signal ED, which is sent to the telephone set 2 side. The telephone set 2 detects it and obtains an envelope signal ES through dialing operation to send it to the switchboard 1 side. On the basis of the selection of the telephone set 2, the switchboard 1 obtains an envelope signal ER and then sends it to an incoming side telephone set 3. The telephone set 3 obtains an envelope signal EA through answering operation and then sends it to the switchboard 1 to make a connection between the telephone sets 2 and 3. In this state, calling between the telephone sets 2 and 3 is performed by the envelope signal EC containing the call contents as digital data. |
