Telephonic communications – Subscriber line or transmission line interface
Reexamination Certificate
1999-10-29
2003-12-09
Barnie, Rexford (Department: 2643)
Telephonic communications
Subscriber line or transmission line interface
C379S413000, C379S413010, C379S412000, C379S413020
Reexamination Certificate
active
06661894
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a circuit configuration for supplying a telephone subscriber loop with a supply voltage, for transmitting a transmitted signal into the telephone subscriber loop, and for receiving a received signal from the telephone subscriber loop. The invention also relates to a network-side terminal of a telephone subscriber loop having the circuit configuration. The invention furthermore relates to a chip set for supplying a telephone subscriber loop with a supply voltage, for transmitting a transmitted signal into the telephone subscriber loop and for receiving a received signal from the telephone subscriber loop.
A known configuration with which it is possible to supply an ISDN subscriber loop by wiring a semiconductor component, is described below and illustrated in FIG.
3
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A circuit configuration for supplying a subscriber line is known from European Patent Application 0 663 755 A1. That circuit configuration is suitable in a particularly beneficial way for conventional analog subscriber lines. A transfer of that supply concept to ISDN subscriber lines presents problems because of unacceptable power losses generated by that circuit configuration, which does not include a transformer. In the case of an analog subscriber line, an operating time of 1% is assumed, during which it is necessary to supply the subscriber line. In contrast, an operating time of 40% is assumed for ISDN subscriber lines, during which a complete supply of the subscriber line is necessary. In the case of an ISDN telephone subscriber line the supply voltage must also be applied outside the operating time in order to supply the subscriber's network terminal NT with energy in the quiescent mode. Due to analog technology that is used, a fluctuating supply voltage on an analog subscriber line is not critical for the functioning of the total system. However, in the case of an ISDN subscriber line, the connection is broken if the supply to the subscriber's network terminal NT falls below a minimum value. The circuit configuration in European Patent Application 0 663 755 is not suitable for use at an ISDN subscriber line because of a high power loss.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a circuit configuration and a chip set for supplying a telephone subscriber loop with a supply voltage and a network-side terminal of a telephone subscriber loop, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which require as few complex discrete components as possible and thereby guarantee a low power loss.
With the foregoing and other objects in view there is provided, in accordance with the invention, a circuit configuration for supplying a telephone subscriber loop having first and second lines or ends with a supply voltage, for transmitting a transmitted signal into the telephone subscriber loop, and for receiving a received signal from the telephone subscriber loop, the circuit configuration comprising a power supply voltage source having a first terminal and a second terminal across which a supply voltage drops or is applied; a first circuit connected to the first line, the first circuit having first and second supply voltage connections; and a second circuit connected to the second line, the second circuit having third and fourth supply voltage connections; the first supply voltage connection connected to the first terminal of the supply voltage source and the fourth supply voltage connection connected to the second terminal of the supply voltage source.
The advantage of this circuit configuration is that through an appropriate choice of the supply voltage and of the supply voltages of the first and second circuit, on one hand a pre-defined battery voltage can be guaranteed between the ends of the telephone subscriber loop, and on the other hand a wanted or desired signal of the subscriber loop can be applied over the first and second circuits in the range of their supply voltages and can be injected from the subscriber loop. The circuit does not require a transformer for this purpose. The power loss in the first and second circuits is reduced to a minimum because voltage drops generating losses are not oriented on the level of the supply voltage source but rather on the level of the supply voltages of the first and second circuits.
In accordance with another feature of the invention, the voltage between the first and the second supply voltage connections and the voltage between the third and the fourth supply voltage connections of the respective first and second circuits are chosen to be substantially lower than the voltage of the supply voltage. The choice of an especially small supply voltage for the first and second circuits can reduce the power loss of the circuit configuration to a minimum.
In accordance with a further feature of the invention, the first and second circuits each have an output driver circuit which is connected with the respective first and second ends of the subscriber loop. In this way it is possible to apply a wanted signal to the subscriber loop.
In accordance with an added feature of the invention, the first and second circuits also each have a current measuring device which measures the current at the respective first and second ends of the subscriber loop and report the values obtained. In this way a wanted signal can be decoupled from the subscriber loop.
In accordance with a further feature of the invention, the first and second circuits each supply a control signal for controlling the current at the first end and at the second end of the subscriber loop. This signal can be used to control a circuit for limiting overcurrent.
In accordance with an added feature of the invention, the first and second circuits respectively supply a first and a second input signal which correspond to the received signal from the subscriber line, and respectively receive a first and a second output signal which correspond to the transmitted signal in the subscriber line. In this way both the first and the second circuits provide a two-wire to four-wire conversion of the signals. The first and the second input signals and the first and the second output signals thus correspond to the wanted signals on the subscriber loop in the receiving direction, i.e. from the subscriber loop to the circuit configuration, and in the transmitting direction, i.e. from the circuit configuration to the subscriber loop.
In accordance with an additional feature of the invention, the first and second input signals and the first and second output signals are digital signals.
In accordance with yet another feature of the invention, the signals are generated through appropriate analog/digital converters and digital/analog converters in the first and second circuits. The use of digital signals has the advantage that they are easier to regenerate and thus the effect of interference can be minimized.
In accordance with yet a further feature of the invention, the first circuit and the second circuit are laid out identically. This has the advantage that it is only necessary to construct a single circuit which is then suitable for both the first and the second circuits. Similar advantages arise in the fabrication and in the use of the first and the second circuits in a circuit configuration according to the invention.
In accordance with yet an added feature of the invention, there is provided a third circuit which is connected with the first circuit and the second circuit in a dc decoupled way. In this configuration the third circuit provides the output signals and processes the arriving input signals. The dc decoupling has the advantage of permitting the third circuit to be operated at voltage levels which are independent of the voltage levels of the first and second circuits.
In accordance with yet an additional feature of the invention, the dc decoupled connection between the first circuit and the third circuit and between the second circuit and the thir
Barnie Rexford
Greenberg Laurence A.
Mayback Gregory L.
Siemens Aktiengesellschaft
Stemer Werner H.
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