| 摘要 |
1,213,279. Selective signalling. INTERNATIONAL STANDARD ELECTRIC CORP. 29 Feb., 1968 [2 March, 1967], No. 9828/68. Heading G4H. A pulse-code signalling system is characterized in that items of data (e.g. addresses in a multiaccess system) are so coded that each can be recognized unambiguously at a receiver even when several items are transmitted at random times in overlapping relationships. The code utilized is such that each code group of n bit periods contains p pulses, where p is the number of items to be coded, and that the spacing between any two pulses in any code group is different to the spacing between any two pulses in any other code group. Three examples of such a code are described Figs. 1, 6 and 7 for coding respectively three, four and five items of data. Clearly the number of bit-periods required namely twelve, twenty-six and forty-two' respectively, increases rapidly and according to the Specification the codes of this type are only useful for coding less than ten items of data. These codes can be generated by a tapped delay line 11, Fig. 2, which relates to the code shown in Fig. 1, appropriate tappings being mixed 12, 13, 14 as shown. Selected 15, 16, 17 code groups are transmitted 15, 16 and applied to a delay line 18 which has corresponding tappings applied to gates 19, 20, 21. |
