Telephonic communications – Subscriber line or transmission line interface
Reexamination Certificate
1997-11-25
2001-05-29
Chan, Wing F. (Department: 2643)
Telephonic communications
Subscriber line or transmission line interface
C379S093070, C370S468000, C370S524000, C370S535000
Reexamination Certificate
active
06240179
ABSTRACT:
BACKGROUND OF THE INVENTION
Much electronic data processing equipment, e.g. telephones, computers and facsimile machines, makes use of 4-wire digital signals (often referred to in North America as digital data services, or DDSs). Transmission of such signals requires four wires which have no abrupt changes in impedance. For example, if existing telephone lines are to be used for 4-wire digital services, they must undergo testing and modification (often referred to as Class C3 data conditioning). This is a serious disadvantage, even if four telephone lines are available, which is not always the case. In addition, repeaters are often needed. For example, one typical 4-wire signal is a bipolar signal at a transmission rate of up to 56 kbps. Such signals typically need a repeater if the line span exceeds 3000 to 3,650 meters (10,000 to 12,000 feet). A further difficulty is that it is difficult to combine conventional analog telephone service (POTS) with 4-wire digital service.
SUMMARY OF THE INVENTION
We have discovered, in accordance with the present invention, how to transfer a 4-wire digital signal and an analog voice channel signal over a simple 2-wire cable, for example a single twisted pair. Thus, in a first preferred aspect this invention provides a method of converting an analog voice channel signal and a 4-wire digital signal into a single signal which can be transferred over a single twisted pair line, the method comprising the steps of:
a. converting the analog voice channel signal into a first binary signal;
b. converting the 4-wire digital signal into a second binary signal;
c. combining the first binary signal and the second binary signal into a higher rate binary signal; and
d. converting the higher rate binary signal into a 2-wire digital signal.
In a second preferred aspect, this invention provides a method of transferring an analog voice channel signal and a 4-wire digital signal from a first location to a second location over a single twisted pair line between the locations, the method comprising:
e. at one of the locations, converting an analog voice channel signal and a 4-wire digital signal into a 2-wire digital signal by the method of the first aspect of the invention;
f. transferring the 2-wire digital signal from step (e) over the single twisted pair line to the other location; and
g. at the other location,
i. converting the 2-wire digital signal from step (f) to a higher rate binary signal,
ii. separating a first binary signal and a second binary signal from the higher rate binary signal produced in step (g(i)), and
iii. converting the first binary signal obtained in step (g(ii)) into an analog voice channel signal, and converting the second binary signal obtained in step (g(ii)) into a 4-wire digital signal.
Typically, one of the locations will be a telephone company location and the other location will be a customer premises. In most cases, step (g) will recreate the analog and digital signals which were converted in steps (a) and (b), and will do so through the same higher rate binary signal, first binary signal and second binary signal. However, the invention includes the possibility that one or more of the signals in step (g) is related to, but not identical to, the corresponding signal in steps (a) through (d). In most cases, steps (e), (f) and (g) will be carried out at both locations, so that 2-wire digital signals are transferred in both directions down the twisted pair.
In a third preferred aspect, the invention provides apparatus which is suitable for use in the method of the first preferred aspect of the invention and which comprises:
1. means for receiving an analog voice channel signal;
2. means for receiving a 4-wire digital signal;
3 means for converting the analog voice channel signal into a first binary signal;
4. means for converting the 4-wire digital signal into a second binary signal;
5. means for combining the first binary signal and the second binary signal into a higher rate binary signal;
6. means for converting the higher rate binary signal into a 2-wire digital format; and
7. means for transferring the 2-wire digital signal to a single twisted pair line.
In a fourth preferred aspect, the invention provides apparatus which is suitable for use at the other location in the method of the second preferred aspect of the invention and which comprises:
1. means for receiving a 2-wire digital signal;
2. means for converting the 2-wire digital signal into a higher rate binary signal;
3. means for separating a first binary signal and a second binary signal from the higher rate binary signal;
4. means for converting the first binary signal into an analog voice channel signal; and
5. means for converting the second binary signal into a 4-wire digital signal.
In a fifth preferred aspect, the invention provides apparatus which combines the apparatus of the third and fourth aspects of the invention, and which is , therefore, suitable for use at both locations when signals are transferred in both directions.
REFERENCES:
patent: 4740963 (1988-04-01), Eckley
patent: 4751696 (1988-06-01), Black
patent: 4924492 (1990-05-01), Gitlin et al.
patent: 4993063 (1991-02-01), Kiko
patent: 5303267 (1994-04-01), Gupta
patent: 5459729 (1995-10-01), Bliven
Balatoni Nicholas A.
Erreygers Jan
Chan Wing F.
Terayon Communications Systems, Inc.
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