| 摘要 |
<p>1,001,747. Telegraphy. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. May 12, 1964 [May 15, 1963], No. 19741/64. Heading H4P. In a data transmission system a synchronizing signal sent with the data is extracted at the receiver by feeding the received signal to a circuit having a quadratic output response and passing the resultant signal to a tuned filter. At the transmitter data pulses, Fig. 3a, are combined with the sync. signal c, and filtered. The resultant waveform f is transmitted. At the receiver, Fig. 2, the demodulated combined signal passes to quadratic response unit 13 which feeds filter 14, whose output is as g and has a frequency twice that of the sync. signal. After a 90 degrees phase shift and limiting, the signal h is inverted at 19, differentiated at 17, 20, and rectified at 18, 21, the outputs being j and k respectively. Waveform k is fed to toggle 22 whose output m passes to tuned filter 23. The filter output n is the inverse of the sync. component in the received signal, so by adding n to the signal the original data is derived, which is retimed at 10 in association with clock signal j. Should toggle 22 start in the wrong phase, signal n will be in the wrong phase, and will result in the output of 9 being of excessive value. To correct for this the arrangement of either Fig. 5 (not shown) or Fig. 6 (not shown) may be used. In the first of these there are two paths, one containing the received signal and the signal n and the other the received signal and the inverse of n. The amplitudes of the signals in the paths are compared and the one of lesser amplitude fed to the retiming unit. In the second arrangement, detection of an excessive amplitude at the output of 9, Fig. 2, causes a pulse from j to be inserted in k so that toggle 22 reverses its phase.</p> |
