Interactive video text telephone communication system - transmits audio commentary during intervals between consecutive picture frame transfers

摘要

Specific frames may be requested by the subscriber over the telephone through code transmission. As picture data are held in a recirculator store to produce a steady image there is ample channel capacity for supplementing the visual information by an audible one. Pref. two buffer stores are used - one for video data (BT) and another for compressed digitised audio data (bt). During video intervals the latter is clocked out at a bit rate of 1.2 k bits p.s. and passed after digit-to-analogue conversion over the switch (TtU) to the telephone exchange (FeVSt) and from there to the individual subscriber (Tln). The analogue data can be used directly in a loudspeaker whereas the video data - at appropriate moments determined by the code controlled switch (UTt) - convert the slow analogue signals into digital signals for entry into a buffer store (BT Dec) where they are recoded for t.v. use and recirculated to produce a steady image.