| 摘要 |
Videotex terminal, supervised by a logic unit (8) with processor and incorporating at least one modem (16) linked by a duplexer (13) and a transformer (9) to a telephone line (2), via unpluggable connection means (3). The logic unit (8) includes means for triggering the production of surveillance pulses by loop opening, these surveillance pulses have a duration which is chosen so as to be able to be detected by the alternating frequency detector (20) of the modem, in such a way that the logic unit can interrupt a call procedure in progress in the event of non-detection by this detector of such a surveillance pulse, the production of which it has triggered. <IMAGE>
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