| 摘要 |
<p>1307655 Multiplex radio signalling INTERNATIONAL STANDARD ELECTRIC CORP 19 April 1971 [16 April 1970] 26303/71 Addition to 1306467 Heading H4L The TV system disclosed in the parent Specification is modified in that an additional synchronizing signal relating to the timecompressed audio signal or signals is transmitted during the period between the end of each frame and the start of the next frame together with the corresponding audio signals and is used at the receiver to select and store at least one of the time-compressed audio signals. As shown in Fig. 2, this synchronizing signal 12 is transmitted between post-equalizing pulses 11 following the frame sync. pulses 10 in the frame blanking interval and first and second audio signals 14, 15 are transmitted during the sweep period of lines following the line sync. pulses 13 in the frame blanking interval. At the receiver, Fig. 1, the incoming signal is fed to a phase comparator 2 which receives a comparison signal from an oscillator 3. The output of the comparator is supplied via a switch 6, which is closed only during the transmission of the additional sync. signal, and filter RC to control the frequency of oscillator 3 the output of the oscillator being frequencymultiplied at 4 to sample the time-compressed audio signals for feeding to a store from which they will be read out at a slow rate. A switch 7 is operated by integrated frame sync. pulses (16, Fig. 2) to connect a circuit 8 tuned to the frequency of the sync. signal 12 and the output of circuit 8 is rectified at 9 to operate switch 6 which operates at level 17, Fig. 2.</p> |
