| 摘要 |
PURPOSE:To make it possible to use efficiently a subscriber's telephone circuit by using the telephone circuit even data transmission by automatically switching the telephone circuit from a subscriber's telephone set to a data transmitter-receiver. CONSTITUTION:Central office CENT is connected to subscribers SUB1-SUBn via telephone office SO and telephone circuits, and data from broadcast station BC are transmitted to television sets. Decoders DEC of those subscribers SUB1-SUBn are provided with telephone circuit interfaces TL1 equipped with circuit switching unit LX, circuit switching controller LC and automatic answering unit AR, and central office CENT is also provided with telephone circuit interface TL2 equipped with automatic calling unit AD and automatic calling controller ADC. Within an allotted time, controller LC of decoder DEC switches the telephone circuit from telephone set TEL to MODEM MOD1 of a data transmitter-receiver and at the allotted time, central office CENT call broadcast station BC to transmit data of broadcast station BC via the telephone circuit. |
