Multiplex communications – Wide area network – Packet switching
Patent
1982-06-21
1985-06-04
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
375110, H04J 306
Patent
active
045218838
ABSTRACT:
A telephony audio signal is transmitted as a digital signal by a transmitter that derives: (1) a master clock of frequency F.sub.MC, (2) a time slot signal of frequency F.sub.TS =F.sub.MC .div.2.sup.N', and (3) a transmit control signal of frequency F.sub.WT =F.sub.MC .div.2.sup.N. The frequencies F.sub.TS and F.sub.WT control the digital signal transmission frequency. A receiver responsive to the digital signal derives the master clock frequency and includes a switched capacitor filter. The receiver derives a reception synchronization signal having a frequency F.sub.RS that is much lower than and asynchronous with the master clock frequency but which has approximately the same frequency as the time slot signal. In response to the information signal and the master clock frequency at the receiver and to the reception synchronization signal, a pulse amplitude modulated signal indicative of the information signal to which the receiver is responsive is supplied to the switched capacitor filter. In response to the master clock frequency at the receiver and the reception synchronization signal a switching control signal for the filter is derived. The filter is switched a predetermined number of times during each period of the reception synchronization signal. The switching times undergo discrete phase jumps that occur at times such that the filter is switched in a plesiosynchronous manner with the reception synchronization signal.
REFERENCES:
patent: 3649757 (1972-03-01), McNeilly et al.
patent: 3732376 (1973-05-01), Chatelon
patent: 4124778 (1978-11-01), Amass
S. Maskara, "Novel Synchronization Scheme for Rate Half Convolutional", IE(I) Journal-ET, vol. 61, Apr. 1981, pp. 80-82.
Chin Wellington
Olms Douglas W.
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