Ground key detector for a SLIC
AssigneeHarris Corporation
InventorGerald M. Cotreau
Life of this patent
Estimating the term…
Abstract
A ground key detector for a subscriber line interface circuit (SLIC) uses information from the tip and ring voltage sensing resistor RS1 and RS2 to determine whether the ring side of the telephone line has been grounded, as when a ground key or fault occurs. The voltage difference between a tip voltage and ground is converted to a DC tip current, and the voltage difference between a ring voltage and a battery voltage is converted to a DC ring current, and the DC ring current is compared to a combination of the DC tip current and a reference current to determine whether the ring side of the telephone system has been grounded. The DC tip and ring currents may also be used to determine whether a fault exists in the tip side of the telephone line, and in the hybrid circuitry of the SLIC.
Claims35
A ground key detector for a subscriber line interface circuit (SLIC), the SLIC having a first current mirror for providing a current proportional to a tip voltage and a second current mirror for providing a current proportional to a ring voltage, the detector comprising:
- a first DC filter for providing a DC tip current proportional to a DC component of the current from the first current mirror;
- a second DC filter for providing a DC ring current proportional to a DC component of the current from the second current mirror;
- a source of reference current;
- a first comparator for comparing the DC ring current to a combination of the DC tip current and the reference current, and for indicating that a ground key has been detected based on the result of the comparison.
An integrated circuit SLIC comprising a portion of a ground key detector, wherein said ground key detector comprises a first DC filter for providing a DC tip current proportional to a DC component of tip voltage, and a second DC filter for providing a DC ring current proportional to a DC component of ring voltage, and wherein said ground key detector further comprises a source of reference current, and a comparator for comparing the DC ring current to a combination of the DC tip current and the reference current.
A ground key detector for a SLIC comprising:
- a source of reference current;
- means for converting a voltage difference between a tip voltage and ground to a tip current;
- means for converting a voltage difference between a ring voltage and a battery voltage to a ring current;
- and
- a comparator for comparing the ring current to a combination of the tip current and the reference current.
A fault detector for a SLIC comprising:
- a source of reference current;
- means for converting a voltage difference between a tip voltage and ground to a tip current;
- means for converting a voltage difference between a ring voltage and a battery voltage to a ring current;
- and
- a comparator for comparing the tip current to a combination of the ring current and the reference current.
A current mode SLIC with a ground key detector and fault detector, said SLIC comprising:
- a first current mirror for providing a current proportional to a SLIC tip voltage;
- a second current mirror for providing a current proportional to a SLIC ring voltage;
- a hybrid circuit for providing a battery feed for a telephone line;
- said ground key detector comprising:
- a first combination DC filter and current mirror for providing a DC tip current proportional to a DC component of the current from the first current mirror;
- a second combination DC filter and current mirror for providing a DC ring current proportional to a DC component of the current from the second current mirror;
- means for providing the DC tip current and the DC ring current to the SLIC for use in said hybrid circuit;
- a source of reference current;
- a first comparator for comparing the DC ring current to a combination of the DC tip current and the reference current, and for indicating that a ground key has been detected when the DC ring current is greater than the combination of the DC tip current and the reference current;
- and said fault detector comprising:
- a second comparator for comparing the DC tip current to a combination of the DC ring current and the reference current, and for indicating that a fault has been detected when the DC tip current is greater than the combination of the DC ring current and the reference current.
A method of detecting a ground key in a SLIC, the SLIC having a first current mirror providing a current proportional to a tip voltage and a second current mirror providing a current proportional to a ring voltage, the method comprising the steps of:
- providing from a first DC filter a DC tip current proportional to a DC component of the current from the first current mirror;
- providing from a second DC filter a DC ring current proportional to a DC component of the current from the second current mirror;
- providing a reference current;
- comparing the DC ring current to a combination of the DC tip current and the reference current in a first comparator;
- and
- indicating that a ground key has been detected based on the result of the comparison.
A method of detecting a ground key in a SLIC comprising the steps of:
- converting a voltage difference between a tip voltage and ground to a tip current, and converting a voltage difference between a ring voltage and a battery voltage to a ring current;
- and
- comparing the ring current to a combination of the tip current and a reference current.
A method of detecting a fault in a SLIC comprising the step of:
- converting a voltage difference between a tip voltage and ground to a tip current, and converting a voltage difference between a ring voltage and a battery voltage to a ring current;
- and
- comparing the tip current to a combination of the ring current and a reference current.
A method of detecting a fault in a SLIC comprising the steps of:
- converting a voltage difference between a tip voltage and ground to a tip current, and converting a voltage difference between a ring voltage and a battery voltage to a ring current;
- and
- comparing the ring current to a combination of the tip current and a reference current.
A method of detecting a fault in a SLIC comprising the steps of:
- converting a voltage difference between a tip voltage and ground to a tip current, and converting a voltage difference between a ring voltage and a battery voltage to a ring current;
- and
- converting the tip current and the ring current to voltage signals related to each;
- and
- comparing the voltage signals.
Dependencies are inferred from the claim text.