| 摘要 |
PURPOSE:To obtain a telephone set with ease of handling by switching automatically a signal into a pushbutton signal at a prescribed time elapsed after a dial pulse is transmitted by the operation of dial keys, displaying the switching and transmitting the pushbutton signal. CONSTITUTION:In hooking off a handset, a hook switch 7 is operated to input an off-hook signal to a control circuit 6, and when a dial key 1 is operated, the circuit 6 transmits a DP signal to a dial pulse DP signal transmission circuit 2. In transmitting a control signal to the polarity detection circuit 4, the circuit 4 detects the polarity inversion of a trunk link when a called party responds and transmits a detection signal to the circuit 6. The circuit 6 uses the detection signal to light a display light 5 and switches the circuit into a pushbutton PB signal transmission circuit 3, from with a PB signal is transmitted. Thus, the PB signal is transmitted to the DP line with ease of operation so as to attain the service of telephone computing or seat reservation of the Japan National Railway Co. |
