Telephonic communications – With usage measurement – Call charge metering or monitoring
Reexamination Certificate
1998-09-16
2001-10-02
Tieu, Binh K. (Department: 2643)
Telephonic communications
With usage measurement
Call charge metering or monitoring
C379S122000, C379S144080, C370S494000
Reexamination Certificate
active
06298124
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for transmitting data signals on analog subscriber lines between subscriber terminal equipment and a telephone exchange, preferably during the speech signal transmission of an existing telephone connection.
2. Description of the Prior Art
A variety of different methods are applied for transmitting data on analog subscriber lines that primarily serve the speech signal transmission between a piece of telephone terminal equipment and the telephone exchange. Among them is a DC signalization wherein the data signal transmission occurs by means of sequences of loop interruptions and a loop signalization that is balanced, or imbalanced, to ground is provided. An AC signalization is also suitable wherein AC signals of 50 Hz are coupled onto the subscriber line loops in ground-imbalanced fashion. Another type of data transmission is what is known as DTMF signalization (multi-frequency code signalization), wherein the signaling information is formed by means of an m out of n coding of n tone frequency signals. Finally, there are what are known as modem transmissions, for which the binary data signals are converted into technically advantageous line signals which correspond to the electrical conditions of analog connections; i.e., frequency modulation, phase difference modulation and quadrature amplitude modulation being essentially suitable for this purpose. The DC signalization is disadvantageous since it disturbs the speech transmission. The AC signalization is extremely slow and thus suitable only for certain types of data transmissions. The two latter methods for data exchange use the speech frequency range and are thus unsuitable for a simultaneous transmission of data and speech. However, there is a need for this, particularly in connection with functions offered by modem convenience subscriber terminal equipments.
It is thus an object of the present invention to propose a method for the transmission of data signals on analog subscriber lines wherein such transmission can also occur during the speech signal transmission and can be implemented with relatively low outlay.
SUMMARY OF THE INVENTION
Such object is achieved in a method of transmission wherein data signals are modulated in both the subscriber circuit of a telephone exchange and in the subscriber terminal equipment onto a signal with periodic characteristics serving as a carrier signal which has a frequency lying outside the speech band and which is already generated at least in the telephone exchange for some other use. The inventive method can thus make use of an infrastructure that is already present.
According to an embodiment of the present invention, as a signal generated for some other use, a signal transmitted from the telephone exchange to the subscriber for purposes of charge display or charge debiting at the subscriber is applied as a carrier signal for the inventive data transmission.
In order to be able to use the inventive method, there is no special outlay necessary in a telephone exchange wherein a generation and transmission of such charge signals is already provided.
The inventive method opens the possibility of offering new performance features. Thus, according to an embodiment of the present invention, information can be transmitted as data signals during the speech signal transmission which serves the authentication of the subscriber terminal equipment and offers a more extensive security against improper use of subscriber-specific facilities than methods wherein the authentication is carried out only in the course of the buildup of a telephone connection.
According to another embodiment of the present invention, the inventive method opens the possibility of specifying the charge display or the charge debiting at the subscriber, which is briefly discussed below.
Further developments of the present invention relate to appropriate circuit arrangements for carrying out the inventive method in both its general and specific form; namely, in connection with its use for subscriber authentication.
Additional features and advantages of the present invention are described in, and will be apparent from, the Detailed Description of the Preferred Embodiments and the Drawings.
REFERENCES:
patent: 4670874 (1987-06-01), Sato et al.
patent: 5303297 (1994-04-01), Hillis
patent: 5506893 (1996-04-01), Buscher et al.
patent: 5608788 (1997-03-01), Demlow et al.
patent: 5822411 (1998-10-01), Swale et al.
patent: 5909445 (1999-06-01), Schneider
patent: 6002755 (1999-12-01), Krank et al.
Bell Boyd & Lloyd LLC
Siemens Aktiengesellschaft
Tieu Binh K.
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