Circuit for supplying power to a network termination unit of a message transmission system
First Claim
1. A circuit for supplying power to a network termination unit of a message transmission system, which is connected to a central station via a subscriber line, said central station including a remote power supply source that supplies power during an emergency operating state, the network termination unit comprising:
- a local power supply voltage source that supplies power during a normal operating state, a direct current converter with a transformer having a clocked switch and a primary winding, which is connected via the clocked switch to the local power supply voltage source, and a first controllable switch, wherein a terminal of the primary winding is connected via the first controllable switch to a wire of the subscriber line.
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Accused Products
Abstract
The invention relates to a circuit for supplying power to a network termination unit (55) of a message transmission system, which is connected to a central station via a subscriber line (30). A local power supply voltage source (41), which is arranged in the network termination unit (55) and which supplies power during a normal operating state, is provided as well as a remote power supply source, which is arranged in the central station and which supplies power during an emergency operating state in the case of a failure or malfunctioning of the local power supply voltage source (41). The network termination unit (55) comprises a direct current converter with a transformer and a clocked switch (20). The primary winding (1) of the transformer is connected via the clocked switch (20) to the local power supply voltage source (41), and a connection of the primary winding (1) is connected via a first controllable switch (5) to a wire of the subscriber line (30).
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Citations
14 Claims
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1. A circuit for supplying power to a network termination unit of a message transmission system, which is connected to a central station via a subscriber line, said central station including a remote power supply source that supplies power during an emergency operating state, the network termination unit comprising:
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a local power supply voltage source that supplies power during a normal operating state, a direct current converter with a transformer having a clocked switch and a primary winding, which is connected via the clocked switch to the local power supply voltage source, and a first controllable switch, wherein a terminal of the primary winding is connected via the first controllable switch to a wire of the subscriber line. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
measuring the amplitude of a local supply voltage and comparing the local supply voltage with a predetermined minimum value, and closing the first controllable switch when the local supply voltage is smaller than the predetermined minimum value, thereby switching the network termination unit from the normal operating state to the remotely supplied state.
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10. A method for switching a network termination unit from a normal operating state to a remotely supplied state by using the switching circuit of claim 2, comprising the steps of:
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measuring the amplitude of a local supply voltage and comparing the local supply voltage with a predetermined minimum value, closing the second controllable switch when the local supply voltage is smaller than the predetermined minimum value, thereby switching the network termination unit from the normal operating state to the remotely supplied state, wherein during the switching of the network termination a charge stored in the buffer capacitor is at least partially supplied to the primary winding of the transformer, and closing the first controllable switch.
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11. The method of claim 9, and further comprising the steps of decreasing the remote supply voltage in the normal operating state from a full value to a predetermined remote value, and increasing the remote supply voltage to the full value when the local supply voltage falls below a predetermined local value or for recharging the buffer capacitor.
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12. The method of claim 10, and further comprising the steps of decreasing the remote supply voltage in the normal operating state from a full value to a predetermined remote value, and increasing the remote supply voltage to the full value when the local supply voltage falls below a predetermined local value or for recharging the buffer capacitor.
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13. The method of claim 9, and further comprising the step of switching the subscriber line into the remotely supplied state for maintenance and test work and returning the subscriber line to the normal operating state after the maintenance and test work has been concluded.
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14. The method of claim 10, and further including switching the subscriber line into the remotely supplied state for maintenance and test work and returning the subscriber line to the normal operating state after the maintenance and test work has been concluded.
Specification