Pulse or digital communications – Repeaters – Testing
Patent
1979-08-30
1982-09-14
Safourek, Benedict V.
Pulse or digital communications
Repeaters
Testing
340347DD, 340349, H04L 300
Patent
active
043499139
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The invention relates to a method and an apparatus for reducing the demand on the number of transferred bits when transferring PCM information.
DESCRIPTION OF PRIOR ART
In a known PCM system, the amplitude level of each sample of the incoming analogue signal is expressed in a binary code, the code being divided into partial codes comprising information concerning, for example, the polarity, the associated segment and the amplitude stage of the signal within the segment of the signal sample, i.e. that quantizing threshold within the segment which is nearest to and lower than the level of the signal sample.
SUMMARY OF THE INVENTION
Characteristic of such a system is that the information concerning to which segment the signal sample belongs always has to be transferred in spite of the fact that a change of segment seldom occurs in comparison with the total number of codings. When transferring PCM information between, for example, subscribers and a local exchange through a subscriber's line, great demands are put on the transfer capacity of the line, from which follows that the more bits which are required in the transferred code, the larger band width necessary. This influences the transmission quality and consequently the length of the transfer distance. Furthermore, the codes become more complicated and more expensive the more bits the code must include.
The invention, which solves the above problem, concerns a method characterized in that amplitude and polarity information are transmitted from a transmitter side to a receiver side, expressed by binary code words without any segment code, information concerning the associated segment being transmitted in the form of segment change information, and if the associated segment is to increase a chosen upper limit value in the amplitude information code word is detected on the transmitter side in order to establish that transit to a higher segment is to occur, and if the associated segment is to decrease a detection is carried out for estabishing that the amplitude information code word is below a chosen lower limit during a determined time in order to decide that transit to a lower segment is to occur, the limit values being transmitted to the receiver side and being used on the transmitter side as well as on the receiver side in order to generate counting signals, which counting signals are registered on the transmitter as well as on the receiver side for giving a value which expresses the segment association and, by means of the registered value, a control signal is generated in order to increase and decrease respectively the segment value of the transmitted signal.
The invention also concerns an arrangement for carrying out the method and is characterized in that it includes, on the transmitter side, a decoder in order to detect in the signal transferred to the receiver side, that the chosen upper limit value in the amplitude information code word has been reached and to detect and to establish by means of a time measuring circuit that the signal value is below the chosen lower limit value of the amplitude code word during a determined time if so a counting up pulse or a counting down pulse being generated respectively, and a first counter which is stepped upwards or downwards respectively by the counting pulses, so that it defines the associated segment of the signal, the values of the counter providing control signals for circuitry included in the arrangement which is influenced by the control signals and in dependence on the same achieves increasing and decreasing respectively of the segment association of the signal sent out, and, on the receiver side, a decoder for detecting the chosen limit values and generating from the values a positive or negative counting pulse, and a second counter which is stepped upwards or downwards respectively by the counting pulses, so that it indicates the segment association of the received signal, the counting values providing control signals for further circuitry included in the means which is in
REFERENCES:
patent: 3678389 (1972-07-01), Heers
patent: 3766542 (1973-10-01), Tomozawa
Chin Stephen
Safourek Benedict V.
Telefonaktiebolaget L M Ericsson
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