| 摘要 |
PURPOSE:To transmit a push-button (PB) signal during the busy state and receive it directly in the other party side by making the transmission of the PB signal possible only when a dialing-system telephone set is hooked off and performing the normal dial originating with dial pulses. CONSTITUTION:When a call signal comes to exchange-side terminals L1 and L2, a bell circuit of the dialing-system telephone set connected to terminals L3 and L4 through this attachment is driven. When the dialing-system telephone set is hooked off, a DC loop is formed, and the service between this telephone set and an originating-side telephone set is permitted. When the DC loop is formed by off-hook, a light emitting diode 1 emits light to make a photodiode 2 conductive. If a PB signal transmitting key 4 is depressed in this state, a corresponding PB signal is generated by a PB signal oscillator 3 and is transmitted directly to the other party through a switching contact 5, the photodiode 2, the light emitting diode 1, and an exchange. |
