Programmable subscriber loop interface circuit and method
OwnerChristopher Ludemaninventor
Life of this patent
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Abstract
A subscriber loop interface circuit and method for externally programming the on-hook, off-hook, and transition states of the subscriber loop interface circuit. The circuit having an off-hook overhead sufficient for long loop applications and having a continuous loop current to loop voltage relationship. The circuit may have plural means for generating reference currents for comparison with loop currents.
Claims20
In a voltage feed, current sense, subscriber loop interface circuit having a pair of subscriber terminals and current sensing means for sensing current flowing through one of said terminals, the improvement comprising:
- (a) first generating means for generating a switch hook detect reference current as a function of a first resistance;
- (b) second generating means for generating upper and lower reference currents by scaling the switch hook detect reference current;
- (c) third generating means for generating a variable control current as a function of an internal reference voltage, a second resistance, and the sensed current;
- and
- (d) voltage control means responsive to the current sensing means for applying a voltage across said terminals, said voltage being continuous over a range of sensed current,
- (i) a first voltage level being applied to indicate an on-hook condition when the sensed current is below the lower reference current,
- (ii) a second voltage level being applied to indicate an off-hook condition when the sensed current is above the upper reference current, and
- (iii) a first variable voltage level being applied as a function of the control current when the sensed current is in between and including the upper and lower reference currents.
In a voltage feed, current sense, subscriber loop interface circuit having a pair of subscriber terminals and current sensing means for sensing current flowing through one of the terminals, a method of supplying power to the subscriber terminals as a function of the sensed current comprising the steps of:
- (a) generating a switch hook detect reference current as a function of a first resistance;
- (b) generating upper and lower reference currents by scaling the switch hook detect reference current;
- (c) generating a variable control current as a function of a second resistance and the sensed current;
- and
- (d) in response to the sensed current, applying a voltage across the terminals, the voltage being continuous over a range of sensed current,
- (i) applying a first voltage across the terminals to indicate an on-hook condition when the sensed current is below the lower reference current,
- (ii) applying a second voltage across the terminals to indicate an off-hook condition when the sensed current is above the upper reference current, and
- (iii) applying a first variable voltage across the terminals as a function of the control current when the current sensed is in between and including the upper and lower reference currents.
In a voltage feed, current sense, subscriber loop interface circuit having a pair of subscriber terminals and current sensing means for sensing current flowing through one of said terminals, the improvement comprising:
- (a) first generating means for generating a switch hook detect reference current as a function of a first resistance;
- (b) second generating means for generating a lower reference current by scaling the switch hook detect reference current;
- (c) third generating means for generating a variable control current as a function of a second resistance and the sensed current;
- (d) fourth generating means for generating an off-hook reference current as a function of a third resistance;
- and
- (e) voltage control means responsive to the current sensing means for applying a voltage across said terminals, said voltage being continuous over a range of sensed current,
- (i) a first voltage level being applied to indicate an on-hook condition when the sensed current is below the lower reference current,
- (ii) a second voltage level being applied to indicate an off-hook condition when the sensed current is above the off-hook reference current, and
- (iii) a first variable voltage level being applied as a function of the control current when the current sensed is in between and including the lower reference current and the off-hook reference current.
In a voltage feed, current sense, subscriber loop interface circuit having a pair of subscriber terminals and current sensing means for sensing current flowing through one of the terminals, a method of supplying power to the subscriber terminals as a function of the sensed current comprising the steps of:
- (a) generating a switch hook detect reference current as a function of a first resistance;
- (b) generating a lower reference current by scaling the switch hook detect reference current;
- (c) generating a variable control current as a function of a second resistance and the sensed current;
- (d) generating an off-hook reference current as a function of a third resistance;
- and
- (e) in response to the sensed current, applying a voltage across the terminals, said voltage being continuous over a range of sensed current,
- (i) a first voltage level being applied to indicate an on-hook condition when the sensed current is below the lower reference current,
- (ii) a second voltage level being applied to indicate an off-hook condition when the sensed current is above the off-hook reference current, and
- (iii) a first variable voltage level being applied as a function of the control current when the current sensed is in between and including the lower reference current and the off-hook reference current.
In an integrated circuit voltage feed, current sense, subscriber loop interface circuit having (i) a pair of subscriber terminals, (ii) current sensing means for sensing current flowing through at least one of said subscriber terminals, and (iii) voltage feed means for supplying an off-hook voltage potential, an on-hook voltage potential, and voltage potential transition between the on-hook and off-hook voltage potentials across said pair of subscriber terminals, the improvement comprising means external to the integrated circuit for programming the off-hook voltage potential, the on-hook voltage potential, and voltage potential transition between the on-hook and off-hook voltage potentials of the subscriber loop interface circuit.
An integrated circuit subscriber loop interface circuit comprising:
- means for sensing a first signal characteristic of a loop signal;
- and
- means external to the integrated circuit for defining a relationship between the first signal characteristic and a second signal characteristic of the loop signal to indicate an on-hook state, an off-hook state, and a transition state of the subscriber loop interface circuit.
Dependencies are inferred from the claim text.