All The Claims

What is claimed is:

1. A storage device for use with a host computer, the device comprising:
at least one rotatable disc having a disc surface with a plurality of physical memory locations, the physical memory locations including data storage locations and attribute storage locations, the attribute storage locations storing protection status information corresponding to data storage locations, wherein the protection status information indicates whether the data storage locations can be written to;
a spindle motor coupled to the disc;
a head configured to read information from the physical memory locations and write information to the physical memory locations;
an actuator which supports the head over the disc surface; and
a disc controller coupled to the spindle motor and the actuator, the controller configured to exchange information with the host computer through an ATA data exchange protocol, to thereby receive write protection commands compatible with the ATA data exchange protocol relating to the write protection status information of at least one physical memory location, and in response executing the write protection commands to implement a write protection scheme compatible with the ATA data exchange protocol.
2. The storage device of claim 1, wherein the controller is further configured to receive an update write protection command compatible with ATA data exchange protocol from the host computer and responsively change the protection status information of at least one physical memory location.
3. The storage device of claim 1 wherein the controller is further adapted to receive an Identify Drive ATA command from the host computer and responsively provide protection status information to the host computer.
4. The storage device of claim 1, wherein the controller is further adapted to read protection status information from the attribute storage locations into a disc buffer memory upon boot-up.
5. The storage device of claim 1, wherein the controller is further adapted to update a disc buffer memory when updating the attribute storage locations to reflect changes made to protection status information.
6. The storage device of claim 1, wherein the controller is adapted to respond to write protection commands only if provided with an appropriate password.
7. The storage device of claim 1, wherein the storage device operates in accordance with ATA-5 specifications.
8. A method of write protecting a storage device having at least one rotatable disc with a disc surface having a plurality of physical memory locations, the physical memory locations including data storage locations and attribute storage locations, the attribute storage locations storing protection status information corresponding to data storage locations, wherein the protection status information indicates whether the data storage locations can be written to, the method comprising the steps of:
(a) receiving, in the storage device, ATA compatible write protection commands from the host computer relating to the write protection status information of at least one physical memory location; and
(b) executing the write protection commands in the storage device to implement an ATA data exchange protocol compatible write protection scheme.
9. The method of claim 8, wherein receiving write protection commands step (a) includes receiving an ATA compatible update write protection command from the host computer, and executing the write protection commands step (b) includes changing the protection status information of at least one physical memory location in response to receiving the ATA compatible update write protection command.
10. The method of claim 8, wherein receiving write protection commands step (a) includes receiving an Identify Drive ATA command from the host computer, and executing the write protection command commands step (b) includes providing protection status information to the host computer in response to the Identify Drive ATA command.
11. The method of claim 8, further comprising reading protection status information from the attribute storage locations into a disc buffer memory upon boot-up.
12. The method of claim 8, further comprising updating a disc buffer memory when updating the attribute storage locations to reflect changes made to protection status information.
13. The method of claim 8, further comprising responding to write protection commands only if provided with an appropriate password.
14. The method of claim 8, wherein the storage device operates in accordance with ATA-5 specifications.
15. A storage device comprising:
means for reading data from and writing data to at least one disc of the storage device; and
means for implementing an ATA compatible write protection scheme.

The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.

We claim:

1. A method of producing a chewing gum product containing a physically-modified bitterness inhibitor in order to control the release rate of the bitterness inhibitor comprising the steps of:
a) mixing a quantity of a bitterness inhibitor with a modifying agent;
b) adding a quantity of the mixture and a bitter medicament to a chewing gum formulation to provide a bitterness inhibitor level in the chewing gum formulation of from about 0.05% to about 8.0%.
2. The method of claim 1 wherein said modifying agent is an encapsulating agent.
3. The method of claim 1 wherein the bitterness inhibitor and encapsulating agent are also mixed with a solvent and the resulting mixture is dried prior to being added to the chewing gum.
4. The method of claim 3 wherein the encapsulating material is selected from the group consisting of maltodextrin and gum arabic.
5. The method of claim 3 wherein the mixture is spray dried and the solvent is selected from the group consisting of alcohol and water.
6. The method of claim 1 wherein a high-potency sweetener selected from the group consisting of aspartame, alitame, salts of acesulfame, cyclamate and its salts, saccharine and its salts, thaumatin, monellin, dihydrochalcones and combinations thereof is mixed in the mixture in combination with the bitterness inhibitor.
7. The method of claim 1 wherein the bitterness inhibitor is selected from the group consisting of ferulic acid, sodium gluconate, sodium ferulate, sodium ascorbate, sodium acetate, sodium glycinate and calcium glycerolphosphate.
8. The method of claim 2 wherein the bitterness inhibitor is fluid-bed coated with a solution of encapsulating agent and solvent in order to decrease the rate of release of the bitterness inhibitor in the chewing gum.
9. The method of claim 8 wherein the solvent is selected from the group consisting of alcohol and water.
10. The method of claim 8 wherein the encapsulating material is selected from the group consisting of shellac and Zein.
11. The method of claim 8 wherein a high-potency sweetener selected from the group consisting of aspartame, alitame, salts of acesulfame, cyclamate and its salts, saccharin and its salts, thaumatin, monellin, dihydrochalcones and combinations thereof is mixed in the mixture in combination with the bitterness inhibitor.
12. The method of claim 8 wherein the bitterness inhibitor is selected from the group consisting of ferulic acid, sodium gluconate, sodium ferulate, sodium ascorbate, sodium acetate, sodium glycinate and calcium glycerol phosphate.
13. The method of claim 2 wherein the bitterness inhibitor is encapsulated by coacervation in order to decrease the rate of release of bitterness inhibitor in chewing gum.
14. The method of claim 2 wherein the bitterness inhibitor is mixed with a molten encapsulating agent and the bitterness inhibitor is encapsulated by spray chilling in order to decrease the rate of release of the bitterness inhibitor in the chewing gum.
15. The method of claim 14 wherein the encapsulating agent comprises wax.
16. The method of claim 2 wherein the bitterness inhibitor is mixed with a polymer as the encapsulating agent and the resulting mixture is extruded into fibers in such a way as to encapsulate the bitterness inhibitor in order to decrease the rate of release of the bitterness inhibitor in the chewing gum.
17. The method of claim 16 wherein the polymer is selected from the group consisting of PVAC, hydroxypropyl cellulose, polyethylene and plastic polymers.
18. A method of producing a chewing gum containing a physically-modified bitterness inhibitor in order to control the release rate of the bitterness inhibitor comprising the steps of:
a) mixing a quantity of the bitterness inhibitor with an agglomerating agent and a solvent to partially coat the bitterness inhibitor;
b) removing the solvent from the mixture of bitterness inhibitor and agglomerating agent to form a dried material; and
c) adding a quantity of the dried material and a bitter medicament to a chewing gum formulation to provide a bitterness inhibitor level in gum of from about 0.05% to about 8.0%.
19. The method of claim 18 wherein the level of coating on the agglomerated bitterness inhibitor is at least about 5%.
20. The method of claim 18 wherein the level of coating on the agglomerated bitterness inhibitor is at least about 15%.
21. The method of claim 18 wherein the level of coating on the agglomerated bitterness inhibitor is at least about 20%.
22. The method of claim 18 wherein the dried material is ground to a powder prior to adding the dried material to the chewing gum.
23. The method of claim 1 wherein the bitterness inhibitor is mixed with an absorbent as the modifying agent.
24. A method of producing a chewing gum product containing a bitterness inhibitor and a bitter medicament comprising the steps of providing a chewing gum product and adding a bitter medicament and a bitterness inhibitor to said product, wherein the bitterness inhibitor is added as a part of a rolling compound applied on the chewing gum product.
25. A method of producing a chewing gum product containing a bitterness inhibitor and a bitter medicament comprising the steps of providing a chewing gum pellet and adding a bitter medicament and a bitterness inhibitor to said product, wherein the bitterness inhibitor is added as a part of a coating on a chewing gum pellet and wherein the bitter medicament is added as part of said pellet, said coating, or both said pellet and said coating.
26. The method of claim 1 wherein the bitterness inhibitor comprises sodium gluconate.
27. A chewing gum product made according to the method of claim 1.
28. The method of claim 1 wherein the bitterness inhibitor is selected from the group consisting of glucono delta lactone; sodium gluconate; potassium gluconate; calcium chloride; neodiosmin; cyclotetradecenones; sclareolide; natural soy flavor; N-sulfomethyl-N-arylureas; sodium, potassium and ammonium salts of ferulic acid and caffeic acid; 2, 4-dihydroxy benzoic acid; ferulic acid; sodium ascorbate; sodium acetate; sodium glycinate; calcium glycerolphosphate; sodium glycerolphosphate and mixtures thereof.
29. The method of claim 18 wherein the bitterness inhibitor is selected from the group consisting of glucono delta lactone; sodium gluconate; potassium gluconate; calcium chloride; neodiosmin; cyclotetradecenones; sclareolide; natural soy flavor; N-sulfomethyl-N-arylureas; sodium, potassium and ammonium salts of ferulic acid and caffeic acid; 2, 4-dihydroxy benzoic acid; ferulic acid; sodium ascorbate; sodium acetate; sodium glycinate; calcium glycerolphosphate; sodium glycerolphosphate and mixtures thereof.
30. The method of claim 24 wherein the bitterness inhibitor is selected from the group consisting of glucono delta lactone; sodium gluconate; potassium gluconate; calcium chloride; neodiosmin; cyclotetradecenones; sclareolide; natural soy flavor; N-sulfomethyl-N-arylureas; sodium, potassium and ammonium salts of ferulic acid and caffeic acid; 2, 4-dihydroxy benzoic acid; ferulic acid; sodium ascorbate; sodium acetate; sodium glycinate; calcium glycerolphosphate; sodium glycerolphosphate and mixtures thereof.
31. The method of claim 25 wherein the bitterness inhibitor is selected from the group consisting of glucono delta lactone; sodium gluconate; potassium gluconate; calcium chloride; neodiosmin; cyclotetradecenones; sclareolide; natural soy flavor; N-sulfomethyl-N-arylureas; sodium, potassium and ammonium salts of ferulic acid and caffeic acid; 2, 4-dihydroxy benzoic acid; ferulic acid; sodium ascorbate; sodium acetate; sodium glycinate; calcium glycerolphosphate; sodium glycerolphosphate and mixtures thereof.
32. The method of claim 1 wherein the bitter medicament comprises a stimulant.

1. An audio amplifier apparatus, suitable for driving a loudspeaker, the audio amplifier apparatus comprising:
a soft charge unit, coupled to the loudspeaker through an output terminal, and supplying a driving current according to a first control signal to soft charge the loudspeaker, so as to gradually increase a voltage level on the output terminal;
a first amplification module, coupled to the output terminal, receiving an audio signal according to the first control signal, and amplifying the audio signal to output a first amplified signal for driving the loudspeaker, wherein the first amplification module comprises:
a first amplifier, having an input terminal and an output terminal, wherein the input terminal of the first amplifier receives the audio signal, and the output terminal of the first amplifier outputs the first amplified signal; and
a first capacitor, having a first end and a second end, wherein the first end of the first capacitor is coupled to the input terminal of the first amplifier, and the second end of the first capacitor is coupled to the output terminal of the first amplifier;

a second amplification module, coupled to the output terminal, receiving the audio signal according to a second control signal, and amplifying the audio signal to output a second amplified signal for driving the loudspeaker,
wherein the soft charge unit generates the second control signal by comparing the voltage level on the output terminal with a predetermined voltage level,
wherein when the voltage level on the output terminal is smaller than the predetermined voltage level, only the first amplification module amplifies the audio signal in response to the first control signal to output the first amplified signal for driving the loudspeaker,
wherein when the voltage level on the output terminal reaches the predetermined voltage level, only the second amplification module amplifies the audio signal in response to the second control signal to output the second amplified signal for driving the loudspeaker;

a first resistor, having a first end and a second end, wherein the first end of the first resistor is coupled to the output terminal of the first amplifier;
a first switch, having a first terminal and a second terminal, and turned on or off according to the first control signal, wherein the first terminal of the first switch receives the audio signal, and the second terminal of the first switch is coupled to the input terminal of the first amplifier and the first end of the first capacitor; and
a second switch, having a first terminal and a second terminal, and turned on or off according to the first control signal, wherein the first terminal of the second switch is coupled to the second end of the first resistor, and the second terminal of the second switch is coupled to the output terminal of the first amplifier,
wherein when the voltage level on the output terminal is not equal to the predetermined voltage level, the first switch and the second switch are turned on according to the first control signal, and when the voltage level on the output terminal is equal to the predetermined voltage level, the first switch and the second switch are turned off according to the first control signal.
2. The audio amplifier apparatus according to claim 1, wherein a driving capability of the first amplification module is lower than a driving capability of the second amplification module.
3. The audio amplifier apparatus according to claim 1, wherein the predetermined voltage level is equal to 1N of a voltage level of a supply voltage received by the audio amplifier apparatus, wherein N is a positive real number not smaller than 1.
4. The audio amplifier apparatus according to claim 1, wherein when the soft charge unit determines that the voltage level on the output terminal is equal to the predetermined voltage level, the soft charge unit enables the second control signal to allow the second amplification module to receive the audio signal, so as to generate the second amplified signal.
5. The audio amplifier apparatus according to claim 4, wherein when the second control signal is enabled, the first control signal is disabled so that the soft charge unit stops soft charging the loudspeaker and the first amplification module stops receiving the audio signal.
6. The audio amplifier apparatus according to claim 1, wherein the second amplification module comprises:
a second amplifier, having an input terminal and an output terminal, wherein the input terminal of the second amplifier receives the audio signal, and the output terminal of the second amplifier outputs the second amplified signal; and
a second capacitor, having a first end and a second end, wherein the first end of the second capacitor is coupled to the input terminal of the second amplifier, and the second end of the second capacitor is coupled to the output terminal of the second amplifier.
7. The audio amplifier apparatus according to claim 6, wherein the second amplification module further comprises:
a third switch, having a first terminal and a second terminal, and turned on or off according to the second control signal, wherein the first terminal of the third switch receives the audio signal, and the second terminal of the third switch is coupled to the input terminal of the second amplifier and the first end of the second capacitor,
wherein when the voltage level on the output terminal is not equal to the predetermined voltage level, the third switch is turned off according to the second control signal, and when the voltage level on the output terminal is equal to the predetermined voltage level, the third switch is turned on according to the second control signal.
8. The audio amplifier apparatus according to claim 6 further comprising:
a first feedback resistor, having a first end and a second end, wherein the first end of the first feedback resistor receives the audio signal, and the second end of the first feedback resistor is coupled to the input terminals of the first amplifier and the second amplifier; and
a second feedback resistor, having a first end and a second end, wherein the first end of the second feedback resistor is coupled to the second end of the first feedback resistor and the input terminals of the first amplifier and the second amplifier, and the second end of the second feedback resistor is coupled to the soft charge unit and the output terminals of the first amplifier and the second amplifier.
9. The audio amplifier apparatus according to claim 6 further comprising:
a pre-amplifier, having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the pre-amplifier is coupled to the output terminal, the second input terminal of the pre-amplifier is coupled to a predetermined voltage, and the output terminal of the pre-amplifier is coupled to the first amplification module and the second amplification module.
10. The audio amplifier apparatus according to claim 1, wherein the soft charge unit comprises:
a current source, supplying the driving current according to a supply voltage;
a first soft charge switch, having a first terminal and a second terminal, and turned on or off according to the first control signal, wherein the first terminal of the first soft charge switch is coupled to the current source;
a delay capacitor, having a first end and a second end, wherein the first end of the delay capacitor is coupled to the second terminal of the first soft charge switch, and the second end of the delay capacitor is coupled to a ground voltage; and
a delay resistor, having a first end and a second end, wherein the first end of the delay resistor is coupled to the second terminal of the first soft charge switch and the first end of the delay capacitor, and the second end of the delay resistor is coupled to the first amplification module and the second amplification module,
wherein when the first soft charge switch is turned on according to the first control signal, the driving current gradually increases the voltage level on the output terminal by the delay capacitor and the delay resistor.
11. The audio amplifier apparatus according to claim 10, wherein the soft charge unit further comprises:
a second soft charge switch, having a first terminal and a second terminal, and turned on or off according to the first control signal, wherein the first terminal of the second soft charge switch is coupled to the second end of the delay resistor, and the second terminal of the second soft charge switch is coupled to the output terminal.
12. The audio amplifier apparatus according to claim 11, wherein when the soft charge unit determines that the voltage level on the output terminal is not equal to the predetermined voltage level, the first soft charge switch and the second soft charge switch are turned on according to the first control signal, and when the soft charge unit determines that the voltage level on the output terminal is equal to the predetermined voltage level, the first soft charge switch and the second soft charge switch are turned off according to the first control signal.
13. The audio amplifier apparatus according to claim 11, wherein the soft charge unit further comprises:
a comparator, having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the comparator is coupled to a predetermined voltage, the second input terminal of the comparator is coupled to the second terminal of the second soft charge switch and the output terminal, and the output terminal of the comparator outputs a comparison signal, wherein the comparator generates the comparison signal according to a comparison result between the voltage level on the output terminal and the predetermined voltage level; and
a latch, coupled to the output terminal of the comparator, and generating the second control signal by latching the comparison signal.
14. The audio amplifier apparatus according to claim 1, wherein the first control signal and the second control signal are inverse to each other.

The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.

1. An apparatus for measuring electrical isolation between a plurality of POE (Power-Over-Ethernet) conductors in a POE system and earth ground, the apparatus comprising:
an alternating current (AC) generator having a first terminal and a second terminal;
a capacitor having a first terminal coupled to at least one of the POE conductors which normally has high isolation from earth ground and having a second terminal coupled to the first terminal the AC generator;
a current-to-voltage converter having a first terminal coupled to the second terminal of the AC generator having a second terminal coupled to earth ground, and having a third terminal for providing an AC voltage representative of the AC current flowing in the series connected AC generator, capacitor, and current-to-voltage converter;
an AC detector having a first terminal coupled to the third terminal of the current-to-voltage converter and having a second terminal for providing a direct current (DC) voltage representative of the AC current flowing in the series connected AC generator, capacitor, and current-to-voltage converter; and
a comparator having a first terminal coupled to the second terminal of the AC detector, having a second terminal coupled to a reference voltage source, and having a third terminal, wherein the comparator is adapted to change a voltage state of the third terminal as the voltage at the first terminal of the comparator goes above and below the reference voltage at the second terminal of the comparator, and wherein, in a condition of high isolation between the POE conductors and earth ground, the AC current flow in the series connected AC generator, capacitor, and current-to-voltage converter is below the comparison threshold set by the reference voltage such that the comparator output is indicative of high isolation and wherein, in a condition of reduced isolation between the POE conductor and earth ground, the AC current flow in the series connected AC generator, capacitor, and current-to-voltage converter is above the comparison threshold set by the reference voltage such that the comparator output is indicative of isolation loss.
2. The apparatus of claim 1, wherein the current-to-voltage converter is a transformer.
3. The apparatus of claim 1, wherein the current-to-voltage converter is a resistor.
4. The apparatus of claim 1, wherein the apparatus further comprises a second comparator having a first terminal coupled to the second terminal of the AC detector, having a second terminal coupled to a second reference voltage, and having a third terminal, wherein the second comparator is adapted to change a voltage state of the third terminal as the voltage at the first terminal of the second comparator goes above and below a second reference voltage at the second terminal of the second comparator, wherein the amplitude of the detected AC voltage is compared to the threshold of the second comparator to monitor operational condition of the isolation loss detector circuitry.
5. The apparatus of claim 1, wherein the apparatus further comprises:
a low-pass filter having a first terminal coupled to the third terminal of the current-to-voltage converter and a second terminal; and
a synchronous rectifier having a first terminal coupled to a second terminal of the low-pass filter, wherein the AC voltage present at the output of the current-to-voltage converter is filtered to reduce interference, then converted to a DC voltage by synchronous rectification, and wherein the filtered and rectified signal is compared with a threshold voltage to determine if isolation loss has occurred.
6. The apparatus of claim 5, wherein the apparatus further comprises an integrator which averages the amplitude of the rectified voltage over many cycles of the AC generator, wherein interference from other AC signals at lower frequencies than the frequency of the AC generator is reduced.
7. An apparatus for measuring electrical isolation between a plurality of POE (Power-Over-Ethernet) conductors in a POE system and earth ground, the apparatus comprising:
an AC generator having a first terminal and a second terminal;
a first capacitor having a first terminal coupled to at least one of the POE conductors which normally has high isolation from earth ground and having a second terminal coupled to the first terminal of the AC generator;
a second capacitor having a first terminal coupled to the first terminal of the first capacitor and to the POE conductor;
an AC detector having a first terminal coupled to the second terminal of the second capacitor and having a second terminal for providing a DC voltage representative of the AC voltage present on the POE conductor; and
a comparator having a first terminal coupled to the second terminal of the AC detector, having a second terminal coupled to a reference voltage, and having a third terminal, wherein the comparator is adapted to change a voltage state of the third terminal as the voltage at the first terminal of the comparator goes above and below the reference voltage at the second terminal of the comparator, and wherein, in a condition of high isolation between the POE conductors and earth ground, the AC voltage present at the first terminal of the AC detector causes a DC voltage at the second terminal of the AC detector which is above the comparison threshold set by the reference voltage such that the comparator output is indicative of high isolation and wherein in a condition of reduced isolation between the POE conductor and earth ground, the AC voltage present at the first terminal of the AC detector causes a DC voltage at the second terminal of the AC detector which is below the comparison threshold set by the reference voltage such that the comparator output is indicative of isolation loss.
8. The apparatus of claim 7, wherein the apparatus further comprises:
a low-pass filter having a first terminal coupled to the second terminal of the second capacitor; and
a synchronous rectifier having a first terminal coupled to a second terminal of the low-pass filter, wherein the AC voltage present at the second terminal of the second capacitor is filtered to reduce interference, then converted to a DC voltage by synchronous rectification, and wherein the filtered and rectified signal is compared with a threshold voltage to determine if isolation loss has occurred.
9. The apparatus of claim 8, wherein the apparatus further comprises an integrator which averages the amplitude of the rectified voltage over many cycles of the AC generator, wherein interference from other AC signals at lower frequencies than the frequency of the AC generator is reduced.
10. A method for measuring electrical isolation between a plurality of conductors in a POE (Power-Over-Ethernet) system and earth ground, the method comprising:
injecting an alternating current into at least one of the conductors in the POE system, which current flows between earth ground and the at least one conductor in the POE system;
measuring the amplitude of the injected current;
comparing the amplitude of the injected current to a first reference threshold, wherein, under normal conditions of negligible isolation loss between the at least one conductor of the POE system and earth ground, the amplitude of the injected current is less than the first reference threshold, and in conditions of isolation loss, the injected current is greater than the first reference threshold, and wherein the state of the comparison is indicative of isolation loss.
11. The method of claim 10, wherein the method further comprises:
coupling bypass capacitance between the at least one conductor in the POE system and earth ground; and
comparing the amplitude of the injected current to another reference threshold which is lower than the first reference threshold, wherein, under normal conditions of negligible isolation loss but of increased flow of the injected alternating current caused by the bypass capacitance from the at least one conductor in the POE system to earth ground, the amplitude of the injected current is greater than a second reference threshold such that the state of the comparison to the second another reference threshold is indicative of proper operation of the isolation loss detection circuitry and wherein a decrease of the injected current below the second reference threshold is indicative of a failure of the isolation loss detection circuitry.
12. The method of claim 10, wherein the step of measuring the amplitude of the injected current further comprises:
converting a sample of the injected current to an AC voltage proportional to the injected current;
synchronously rectifying the AC voltage proportional to the injected current by commutating the AC voltage signal with a switching signal coupled from the generator of the injected current, the switching signal having the same frequency and a stable phase compared to the AC voltage proportional to the injected current; and
integrating over a time period the rectified output of the synchronously rectifying the AC voltage step, wherein a DC voltage responsive to the amplitude of the injected current is generated, and wherein noise on the injected current is rejected.
13. An apparatus for measuring electrical isolation between a plurality of POE (Power-Over-Ethernet) conductors in a POE system and earth ground, the apparatus comprising:
a transformer having primary and secondary windings, having a first primary terminal, having a second primary terminal coupled to earth ground, having a third secondary terminal, and having a fourth secondary terminal coupled to local system ground;
a capacitor having a first terminal coupled to at least one of the POE conductors which normally has high isolation from earth ground and having a second terminal coupled to the first primary terminal of the transformer;
an AC generator having a first terminal coupled to local system ground and having a second terminal coupled to a first terminal of a resistor;
a second terminal of the resistor coupled to the third secondary terminal of the transformer;
an AC detector having a first terminal coupled to the second terminal of the AC generator and the first terminal of the resistor, having a second terminal coupled to the second terminal of the resistor and the third secondary terminal of the transformer, and having a third output terminal upon which is present a DC voltage representative of the AC current flowing in the series connected AC generator, resistor and transformer secondary; and
a comparator having a first terminal coupled to the third output terminal of the AC detector, having a second terminal coupled to a reference voltage, and having a third terminal which changes voltage state as the voltage at the first terminal of the comparator goes above and below the reference voltage at the second terminal of the comparator, wherein, in a condition of high isolation between the POE conductors and earth ground, the impedance across the secondary winding of the transformer is relatively high, being responsive to the impedance across the primary winding of the transformer, causing a relatively low AC current to flow in the resistor and further causing the output of the AC detector to be below the comparison threshold set by the reference voltage such that the comparator output is indicative of high isolation, and wherein, in a condition of reduced isolation between the POE conductors and earth ground, the impedance across the secondary winding of the transformer is relatively low, being responsive to the impedance across the primary winding of the transformer, causing a relatively high AC current to flow in the resistor and further causing the output of the AC detector to be above the comparison threshold set by the reference voltage such that the comparator output is indicative of low isolation.
14. A method for measuring electrical isolation between a plurality of conductors in a POE (Power-Over-Ethernet) system and earth ground, comprising the steps:
coupling a first terminal of the primary of a transformer through a capacitor to conductors of the POE system,
coupling a second terminal of the primary of the transformer to earth ground, wherein the impedance of the secondary of the transformer is responsive to the impedance between at least one of the conductors of the POE system and earth ground;
coupling an AC signal through a series connection of the secondary of the transformer and a series resistor;
measuring the amplitude of the resulting AC voltage across the resistor;
comparing the amplitude of the AC voltage to a reference threshold, wherein, under normal conditions of negligible isolation loss between the at least one conductor of the POE system and the earth ground, the amplitude of the AC voltage is less than the reference threshold, and in conditions of isolation loss, the AC voltage is greater than the first reference threshold, and wherein the state of the comparison is indicative of isolation loss.