| 摘要 |
<p>The system comprises a television transmitter able to broadcast a television signal and interactivity information, user devices consisting of a television set 9, a decoder 30 connected to it, and a device 10 for direct and automatic access to the telephone line, one or more service centres CS connected to a node of a data network ITAPAC, or connected to the national telephone network POTS, possibly via the Audiotex service. The device 10 for direct and automatic access to the telephone line is able to exchange messages with the service centre CS1 connected to it by means of a data network Itapac via two types of frames, respectively, a frame of data type or DATA FRAME and a frame of acknowledged type or ACKNOWLEDGED FRAME. Said device 10 is also able to exchange messages with the service centre CS2 and CS3 connected to it by means of the national telephone network POTS via a sequence of DTMF tones which constitute a data frame or DTMF DATA FRAME and via a DTMF tone which constitutes a confirmation. <IMAGE></p> |
