Inline power-based common mode communications in a wired data telecommunications network

• US 8,300,666 B2
• Filed: 10/07/2004
• Issued: 10/30/2012
• Est. Priority Date: 10/07/2004
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Karam, Roger A., Schindler, Frederick R., Diab, Wael William
• Primary Examiner(s): Jagannathan, Melanie
• Assistant Examiner(s): Chu, Wutchung
• Application Number:
  US10/961,904
• Publication Number:
  US 20060082220A1
• Time in Patent Office: 2,945 Days
• Field of Search: 307 1- 4, 307/28, 307/43, 340/310.11, 340/310.12, 340/310.16, 713/300, 324/98
• US Class Current: 370/496
• CPC Class Codes: H02J 13/00009 using pulsed signals
• CPC Class Codes: H02J 13/0001 using modification of a parameter of the network power signal
• CPC Class Codes: H02J 13/00012 using an auxiliary transmission line
• CPC Class Codes: H02J 13/00018 using phone lines

Abstract

Communications over a wired data telecommunications network between and among power sourcing equipment (PSE), powered devices (PDs), and the like, take place over the wired medium by modulating an inline power signal. Any suitable communications protocol may be used and any suitable modulation scheme can be used. Examples of information to be communicated include: changing power requirements or capabilities (higher or lower) and acknowledgements thereof (permitting finer power class gradation than available under existing standards); sensor data; wireless data converted to wired data; status signaling, and the like. Such communications may be used for a number of purposes including supporting redundant provision of services over a network.

Claims

1. A method for communicating a message from a powered device (PD) to power sourcing equipment (PSE) in a wired data telecommunications network, the method comprising:

performing a PD detection and classification to verify that the PD is configured to be supplied with inline power from the PSE;

responsive to said performing, establishing an initial inline power relationship between the PD and the PSE so that the PD is receiving an initial minimum level of power from the PSE; and

current modulating the inline power at the PD with a predetermined communications protocol to communicate the message from the PD to the PSE;

wherein establishing the initial inline power relationship comprises biasing a first pair of conductors with one direct current (DC) voltage level and a second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage, the PD and PSE being powered by the difference voltage, and the difference voltage exceeding 20 Volts,

wherein the message includes a request for a different minimum level of power from the PSE to the PD,

and further comprising, responsive to said current modulating, providing the different minimum level of power from the PSE to the PD,

wherein the first pair of conductors are used for performing at least the function of transmitting data from the PD to the PSE, and the current modulating will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

2. The method of claim 1, wherein:

the PD is a voice over internet protocol telephone and the PSE is a switch.

3. An apparatus for communicating a message from a powered device (PD) to power sourcing equipment (PSE) in a wired data telecommunications network, the apparatus comprising:

means for performing a PD detection and classification to verify that the PD is configured to be supplied with inline power from the PSE;

means responsive to said means for performing, for establishing an initial inline power relationship between the PD and the PSE so that the PD is receiving an initial minimum level of power from the PSE; and

means for current modulating the inline power at the PD with a predetermined communications protocol to communicate the message from the PD to the PSE;

wherein means for establishing the initial inline power relationship comprises means for biasing a first pair of conductors with one direct current (DC) voltage level and a second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage, the PD and PSE being powered by the difference voltage, and the difference voltage exceeding 20 Volts,

wherein the message includes a request for a different minimum level of power from the PSE to the PD,

and further comprising means responsive to said current modulating for providing the different minimum level of power from the PSE to the PD,

wherein the first pair of conductors are used for performing at least the function of transmitting data from the PD to the PSE, and the means for current modulating will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

4. The apparatus of claim 3, wherein:

the PD is a voice over internet protocol telephone and the PSE is a switch.

5. A system for communicating a message from a powered device (PD) to power sourcing equipment (PSE) in a wired data telecommunications network, the system comprising:

circuitry for performing a PD detection and classification to verify that the PD is configured to be supplied with inline power from the PSE;

circuitry responsive to said circuitry for performing, for establishing an initial inline power relationship between the PD and the PSE so that the PD is receiving an initial minimum level of power from the PSE; and

circuitry for current modulating the inline power at the PD with a predetermined communications protocol to communicate the message from the PD to the PSE;

wherein circuitry for establishing the initial inline power relationship comprises circuitry for biasing a first pair of conductors with one direct current (DC) voltage level and a second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage, the PD and PSE being powered by the difference voltage, and the difference voltage exceeding 20 Volts,

wherein the message includes a request for a different minimum level of power from the PSE to the PD,

and further comprising circuitry responsive to said current modulating for providing the different minimum level of power from the PSE to the PD,

wherein the first pair of conductors are used for performing at least the function of transmitting data from the PD to the PSE, and the circuitry for current modulating will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

6. The system of claim 5, wherein:

the PD is a voice over internet protocol telephone and the PSE is a switch.

7. A method for communicating a message from power sourcing equipment (PSE) to a powered device (PD) in a wired data telecommunications network, the method comprising:

performing a PD detection and classification to verify that the PD is configured to be supplied with inline power from the PSE;

responsive to said performing, establishing an initial inline power relationship between the PD and the PSE so that the PD is receiving an initial minimum level of power from the PSE; and

voltage modulating the inline power at the PSE with a predetermined communications protocol to communicate the message from the PSE to the PD;

wherein establishing the initial inline power relationship comprises biasing a first pair of conductors with one direct current (DC) voltage level and a second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage, the PD and PSE being powered by the difference voltage, and the difference voltage exceeding 20 Volts,

wherein the message includes a confirmation of a request for a different minimum level of power from the PSE to the PD,

and further comprising, responsive to said voltage modulating, providing the different minimum level of power from the PSE to the PD,

wherein the first pair of conductors are used for performing at least the function of transmitting data from the PD to the PSE, and the voltage modulating will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

8. The method of claim 7, wherein:

the PD is a voice over internet protocol telephone and the PSE is a switch.

9. An apparatus for communicating a message from power sourcing equipment (PSE) to a powered device (PD) in a wired data telecommunications network, the apparatus comprising:

means for performing a PD detection and classification to verify that the PD is configured to be supplied with inline power from the PSE;

means responsive to said means for performing, for establishing an initial inline power relationship between the PD and the PSE so that the PD is receiving an initial minimum level of power from the PSE; and

means for voltage modulating the inline power at the PSE with a predetermined communications protocol to communicate the message from the PSE to the PD;

wherein means for establishing the initial inline power relationship comprises means for biasing a first pair of conductors with one direct current (DC) voltage level and a second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage, the PD and PSE being powered by the difference voltage, and the difference voltage exceeding 20 Volts,

wherein the message includes a confirmation of a request for a different minimum level of power from the PSE to the PD,

and further comprising means responsive to said voltage modulating for providing the different minimum level of power from the PSE to the PD,

wherein the first pair of conductors are used for performing at least the function of transmitting data from the PD to the PSE, and the means for voltage modulating will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

10. The apparatus of claim 9, wherein:

the PD is a voice over internet protocol telephone and the PSE is a switch.

11. A system for communicating a message from power sourcing equipment (PSE) to a powered device (PD) in a wired data telecommunications network, the system comprising:

circuitry for performing a PD detection and classification to verify that the PD is configured to be supplied with inline power from the PSE;

circuitry responsive to said circuitry for performing, for establishing an initial inline power relationship between the PD and the PSE so that the PD is receiving an initial minimum level of power from the PSE; and

circuitry for voltage modulating the inline power at the PSE with a predetermined communications protocol to communicate the message from the PSE to the PD;

wherein circuitry for establishing the initial inline power relationship comprises circuitry for biasing a first pair of conductors with one direct current (DC) voltage level and a second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage, the PD and PSE being powered by the difference voltage, and the difference voltage exceeding 20 Volts,

wherein the message includes a confirmation of a request for a different minimum level of power from the PSE to the PD,

and further comprising circuitry responsive to said voltage modulating for providing the different minimum level of power from the PSE to the PD,

wherein the first pair of conductors are used for performing at least the function of transmitting data from the PD to the PSE, and the circuitry for voltage modulating will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

12. The system of claim 11, wherein:

the PD is a voice over internet protocol telephone and the PSE is a switch.

13. A powered device (PD) having a requirement for a minimum level of inline power supplied over a wired data telecommunications network from power sourcing equipment (PSE) to which the PD is coupled, the minimum level of inline power requirement subject to change from time to time, the PD comprising:

circuitry for determining a minimum level of inline power required by the PD;

circuitry for current modulating the inline power supplied over the wired data telecommunications network; and

an encoder for encoding a message from the PD to the PSE on the current modulating circuitry communicating a present need for a changed minimum level of inline power,

wherein the wired data telecommunications network includes a first pair of conductors used for performing at least the functions of supplying inline power to the PD from the PSE, encoding the message on the current modulating circuitry, and transmitting data from the PD to the PSE, and the current modulating circuitry will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

14. The apparatus of claim 13, wherein:

the circuitry for current modulating comprises at least one current source.

15. A powered device (PD) having a requirement for a minimum level of inline power supplied over a wired data telecommunications network from power sourcing equipment (PSE) to which the PD is coupled, the minimum level of inline power requirement subject to change from time to time, the PD comprising:

means for determining a minimum level of inline power required by the PD;

means for current modulating the inline power supplied over the wired data telecommunications network; and

means for encoding a message from the PD to the PSE on the current modulating means communicating a present need for a changed minimum level of inline power,

wherein the wired data telecommunications network includes a first pair of conductors used for performing at least the functions of supplying inline power to the PD from the PSE, encoding the message on the current modulating means, and transmitting data from the PD to the PSE, and the current modulating means will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

16. The apparatus of claim 15, wherein:

the means for current modulating comprises at least one current source.

17. The PD of claim 15, wherein:

the PD takes a first amount of time to complete a bootstrap operation after first application of power thereto, and

the determining means, modulating means and encoding means are all operable in less than said first amount of time.

18. A method for operating a powered device (PD) having a requirement for a minimum level of inline power supplied over a wired data telecommunications network from power sourcing equipment (PSE) to which the PD is coupled, the minimum level of inline power requirement subject to change from time to time, the method comprising:

determining a minimum level of inline power required by the PD; and

encoding a message from the PD to the PSE by current modulating the inline power supplied over the wired data telecommunications network to the PD to communicate a need for a changed minimum level of inline power,

wherein the wired data telecommunications network includes a first pair of conductors used for performing at least the functions of supplying inline power to the PD from the PSE, encoding the message by current modulating the inline power, and transmitting data from the PD to the PSE, and the current modulating will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

19. The method of claim 18, wherein:

the current modulating is accomplished using at least one current source.

20. The method of claim 18, further comprising:

bootstrapping the PD for operation, wherein;

the determining, modulating and encoding are able to take place prior to the completion of the bootstrapping.

21. A power sourcing equipment (PSE) device having a capacity to provide up to a first quantity of inline power over a wired data telecommunications network to a powered device (PD) to which the PSE is coupled, the PSE comprising:

circuitry for receiving a request from the PD for a changed minimum level of inline power required by the PD;

circuitry for voltage modulating the inline power supplied over the wired data telecommunications network from the PSE to the PD; and

an encoder for encoding a message from the PSE to the PD on the voltage modulating circuitry communicating a present changed minimum level of inline power to be supplied from the PSE to the PD,

wherein the wired data telecommunications network includes a first pair of conductors used for performing at least the functions of supplying inline power to the PD from the PSE, encoding the message on the voltage modulating circuitry, and transmitting data from the PD to the PSE, and the voltage modulating circuitry will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

22. The apparatus of claim 21, wherein:

the circuitry for voltage modulating comprises at least one transistor or diode.

23. A power sourcing equipment (PSE) device having a capacity to provide up to a first quantity of inline power over a wired data telecommunications network to a powered device (PD) to which the PSE is coupled, the PSE comprising:

means for receiving a request from the PD for a changed minimum level of inline power required by the PD;

means for voltage modulating the inline power supplied over the wired data telecommunications network from the PSE to the PD; and

means for encoding a message from the PSE to the PD on the voltage modulating means communicating a present changed minimum level of inline power to be supplied from the PSE to the PD,

wherein the wired data telecommunications network includes a first pair of conductors used for performing at least the functions of supplying inline power to the PD from the PSE, encoding the message on the voltage modulating means, and transmitting data from the PD to the PSE, and the voltage modulating means will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

24. The apparatus of claim 23, wherein:

the means for voltage modulating comprises at least one transistor or diode.

25. A method for operating a power sourcing equipment (PSE) device having a capacity to provide up to a first quantity of inline power over a wired data telecommunications network to a powered device (PD) to which the PSE is coupled, the method comprising:

receiving a request from the PD for a changed minimum level of inline power required by the PD;

voltage modulating the inline power supplied over the wired data telecommunications network from the PSE to the PD; and

encoding a message from the PSE to the PD with said voltage modulating communicating a present changed minimum level of inline power to be supplied from the PSE to the PD,

wherein the wired data telecommunications network includes a first pair of conductors used for performing at least the functions of supplying inline power to the PD from the PSE, encoding the message with the voltage modulating, and transmitting data from the PD to the PSE, and the voltage modulating will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

26. The method of claim 25, wherein:

the voltage modulating is accomplished using at least one transistor or diode.

27. The method of claim 25, further comprising:

bootstrapping the PSE for operation, wherein;

the receiving, modulating and encoding are able to take place prior to the completion of the bootstrapping.

28. A powered device (PD) for communicating a message to power sourcing equipment (PSE) in a wired data telecommunications network, the PD comprising:

a first circuit for participating in a PD detection and classification process to verify that the PD is configured to be supplied with inline power from the PSE;

a second circuit responsive to said first circuit, for establishing an initial inline power relationship between the PD and the PSE so that the PD is receiving an initial minimum level of power from the PSE; and

a third circuit for current modulating the power at the PD with a predetermined communications protocol to communicate the message from the PD to the PSE;

wherein the second circuit for establishing the initial inline power relationship is configured to bias a first pair of conductors with one direct current (DC) voltage level and a second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage, the PD and PSE being powered by the difference voltage, and the difference voltage exceeding 20 Volts,

wherein the message includes a request for a different minimum level of power from the PSE to the PD,

and wherein the second circuit is further configured, responsive to said current modulating, to provide the different minimum level of power from the PSE to the PD,

and wherein the first pair of conductors are used for performing at least the function of transmitting data from the PD to the PSE, and the third circuit will remain operable to communicate the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

29. A power sourcing equipment (PSE) device for receiving a message from a powered device (PD) in a wired data telecommunications network, the PSE comprising:

a first circuit for participating in a detection and classification process to verify that the PD is configured to be supplied with inline power from the PSE;

a second circuit responsive to said first circuit, for establishing an initial inline power relationship between the PD and the PSE so that the PD is receiving an initial minimum level of power from the PSE; and

a third circuit for demodulating a modulated current signal at the PSE received from the PD to receive the message from the PD at the PSE;

wherein the second circuit for establishing the initial inline power relationship is configured to bias a first pair of conductors with one direct current (DC) voltage level and a second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage, the PD and PSE being powered by the difference voltage, and the difference voltage exceeding 20 Volts,

wherein the message includes a request for a different minimum level of power from the PSE to the PD,

and wherein the second circuit is further configured, responsive to said modulated current signal, to provide the different minimum level of power from the PSE to the PD,

wherein the first pair of conductors are used for performing at least the function of transmitting data from the PD to the PSE, and the third circuit for current demodulating will remain operable to receive the message from the PD to the PSE even if at least one of the following occurs;

(a) one conductor of said first pair of conductors is open, and (b) both conductors of said first pair of conductors are shorted together.

30. A method for communicating a message from a first station via a second station to a third station in a wired data telecommunications network, the first station comprising a powered device (PD), the second station comprising power sourcing equipment (PSE), and the third station comprising a PD, and the wired data telecommunications network having at least a first pair of conductors and a second pair of conductors for coupling the first station to the second station and at least a third pair of conductors and a fourth pair of conductors for coupling the second station to the third station, the method comprising:

biasing the first pair of conductors with one direct current (DC) voltage level and the second pair of conductors with a second DC voltage level, the difference between the first and second voltage levels being a first difference voltage; and

voltage modulating the difference voltage with a predetermined communications protocol to communicate the message from the first station to the second station;

transmitting the message from the first station to the second station;

wherein during said biasing the difference voltage exceeds 20 Volts, wherein the message includes a request for a different minimum level of power from the PSE to the PD,

and further comprising, responsive to said voltage modulating, providing the different minimum level of power from the PSE to the PD,

and further comprising;

biasing the third pair of conductors with the one DC voltage level and the fourth pair of conductors with the second DC voltage level, the difference between the third and fourth voltage levels being a second difference voltage;

modulating the second difference voltage with a predetermined communications protocol to communicate the message from the second station to the third station, the modulating including at least one of current modulating and voltage modulating; and

transmitting the message from the second station to the third station.

31. A method for communicating a message from a first station via a second station to a third station in a wired data telecommunications network, the first station comprising a powered device (PD), the second station comprising power sourcing equipment (PSE), and the third station comprising a PD, and the wired data telecommunications network having at least a first pair of conductors and a second pair of conductors for coupling the first station to the second station and at least a third pair of conductors and a fourth pair of conductors for coupling the second station to the third station, the method comprising:

biasing the first pair of conductors with one direct current (DC) voltage level and the second pair of conductors with a second DC voltage level, the difference between the first and second voltage levels being a first difference voltage; and

current modulating the difference voltage with a predetermined communications protocol to communicate the message from the first station to the second station;

transmitting the message from the first station to the second station;

wherein said modulating takes place while at least one of the first station and the second station is powered by the difference voltage;

wherein during said biasing the difference voltage exceeds 20 Volts,

wherein the message includes a request for a different minimum level of power from the PSE to the PD,

and further comprising, responsive to said current modulating, providing the different minimum level of power from the PSE to the PD,

and further comprising;

biasing the third pair of conductors with the one DC voltage level and the fourth pair of conductors with the second DC voltage level, the difference between the third and fourth voltage levels being a second difference voltage;

modulating the second difference voltage with a predetermined communications protocol to communicate the message from the second station to the third station, the modulating including at least one of current modulating and voltage modulating; and

transmitting the message from the second station to the third station.

32. A method for communicating a message from a first station via a second station to a third station in a wired data telecommunications network, the first station comprising a powered device (PD), the second station comprising power sourcing equipment (PSE), and the third station comprising a PD, and the wired data telecommunications network having at least a first pair of conductors and a second pair of conductors for coupling the first station, the second station and the third station, the method comprising:

biasing the first pair of conductors with one direct current (DC) voltage level and the second pair of conductors with a second DC voltage level, the difference between the first and second voltage levels being a difference voltage; and

voltage modulating the difference voltage with a predetermined communications protocol to communicate the message from the first station to the second station;

transmitting the message from the first station to the second station;

wherein said modulating takes place while at least one of the first station and the second station is powered by the difference voltage;

wherein during said biasing the difference voltage exceeds 20 Volts,

wherein the message includes a request for a different minimum level of power from the PSE to the PD,

and further comprising, responsive to said voltage modulating, providing the different minimum level of power from the PSE to the PD, and further comprising;

current modulating the difference voltage with a predetermined communications protocol to communicate the message from the second station to the third station;

transmitting the message from the second station to the third station.

33. A method for communicating a first message from a first station to a third station and a second message from the second station to the first station in a wired data telecommunications network, a second station providing inline power to the first station and the second station, the first station comprising a powered device (PD), the second station comprising power sourcing equipment (PSE), and the third station comprising a PD, and the wired data telecommunications network having at least a first pair of conductors and a second pair of conductors for coupling the first station, the second station and the third station, the method comprising:

biasing the first pair of conductors with one direct current (DC) voltage level and the second pair of conductors with a second DC voltage level, the difference between the first and second voltage levels being a difference voltage; and

voltage modulating the difference voltage with a predetermined communications protocol to communicate the first message from the first station to the second station;

transmitting the first message from the first station to the second station;

wherein said modulating takes place while at least one of the first station and the second station is powered by the difference voltage;

wherein during said biasing the difference voltage exceeds 20 Volts,

wherein the first message includes a request for a different minimum level of power from the PSE to the PD of the first station,

and further comprising, responsive to said voltage modulating, providing the different minimum level of power from the PSE to the PD of the first station, and further comprising;

current modulating the difference voltage with a predetermined communications protocol to communicate the second message from the second station to the first station;

transmitting the second message from the second station to the first station.

34. A method for communicating a message from a first station to at least one second station in a wired data telecommunications network, the first station and the second station comprising power sourcing equipment (PSE), and the wired data telecommunications network having at least a first pair of conductors and a second pair of conductors for coupling the first station to the at least one second station, the method comprising:

periodically conducting at the first station a first discovery process to determine if a powered device (PD) is present on the wired data telecommunications network, followed by a back off period;

listening during the back off period for a special signature indicating the presence of a PSE at the second station;

detecting the presence of a PSE at the second station; and

communicating, responsive to said detecting, with the PSE at the second station.

35. The method of claim 34, wherein said special signature comprises a unique identity network associated with PSEs.

36. The method of claim 34, wherein said special signature comprises a unique modulated signal associated with PSEs.

37. The method of claim 34, wherein said communicating takes place by modulating an inline power signal between the first station and the second station.

38. The method of claim 37, wherein said modulating includes current modulating.

39. The method of claim 37, wherein said modulating includes voltage modulating.

40. The method of claim 34, further comprising:

biasing the first pair of conductors with one direct current (DC) voltage level and the second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage; and

current modulating a current flowing from the first pair of conductors to the second pair of conductors with a predetermined communications protocol to communicate the message from the first station to the at least one second station.

41. The method of claim 40, wherein said modulating takes place while at least one of the first station and the second station is powered by the difference voltage.

42. An apparatus for communicating a message from a first station to at least one second station in a wired data telecommunications network, the first station and the second station comprising power sourcing equipment (PSE), and the wired data telecommunications network having at least a first pair of conductors and a second pair of conductors for coupling the first station to the at least one second station, the apparatus comprising:

means for periodically conducting at the first station a first discovery process to determine if a powered device (PD) is present on the wired data telecommunications network, followed by a back off period;

means for listening during the back off period for a special signature indicating the presence of a PSE at the second station;

means for detecting the presence of a PSE at the second station; and

means for communicating, responsive to said detecting, with the PSE at the second station.

43. The apparatus of claim 42, wherein said special signature comprises a unique identity network associated with PSEs.

44. The apparatus of claim 42, wherein said special signature comprises a unique modulated signal associated with PSEs.

45. The apparatus of claim 42, wherein said means for communicating modulates an inline power signal between the first station and the second station.

46. The apparatus of claim 45, wherein said means for modulating current modulates.

47. The apparatus of claim 45, wherein said means for modulating voltage modulates.

48. The apparatus of claim 42, further comprising:

means for biasing the first pair of conductors with one direct current (DC) voltage level and the second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage; and

means for current modulating a current flowing from the first pair of conductors to the second pair of conductors with a predetermined communications protocol to communicate the message from the first station to the at least one second station.

49. The apparatus of claim 48, wherein at least one of the first station and the second station is powered by the difference voltage.

50. A system for communicating a message from a first station to at least one second station in a wired data telecommunications network, the first station and the second station comprising power sourcing equipment (PSE), and the wired data telecommunications network having at least a first pair of conductors and a second pair of conductors for coupling the first station to the at least one second station, the system comprising:

circuitry for periodically conducting at the first station a first discovery process to determine if a powered device (PD) is present on the wired data telecommunications network, followed by a back off period;

circuitry for listening during the back off period for a special signature indicating the presence of a PSE at the second station;

circuitry for detecting the presence of a PSE at the second station; and

circuitry for communicating, responsive to said detecting, with the PSE at the second station.

51. The system of claim 50, wherein said special signature comprises a unique identity network associated with PSEs.

52. The system of claim 50, wherein said special signature comprises a unique modulated signal associated with PSEs.

53. The system of claim 50, wherein said circuitry for communicating modulates an inline power signal between the first station and the second station.

54. The system of claim 53, wherein said circuitry for modulating current modulates.

55. The system of claim 53, wherein said circuitry for modulating voltage modulates.

56. The system of claim 50, further comprising:

circuitry for biasing the first pair of conductors with one direct current (DC) voltage level and the second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage; and

circuitry for current modulating a current flowing from the first pair of conductors to the second pair of conductors with a predetermined communications protocol to communicate the message from the first station to the at least one second station.

57. The system of claim 56, wherein at least one of the first station and the second station is powered by the difference voltage.

58. An apparatus for communicating a message from a first station to at least one second station in a wired data telecommunications network, the first station and the second station comprising power sourcing equipment (PSE), and the wired data telecommunications network having at least a first pair of conductors and a second pair of conductors for coupling the first station to the at least one second station, the apparatus comprising:

a discoverer for periodically conducting at the first station a first discovery process to determine if a powered device (PD) is present on the wired data telecommunications network, followed by a back off period;

a receiver for listening during the back off period for a special signature indicating the presence of a PSE at the second station;

a detector for detecting the presence of a PSE at the second station; and

a communicator for communicating, responsive to said detecting, with the PSE at the second station.

59. The apparatus of claim 58, wherein said special signature comprises a unique identity network associated with PSEs.

60. The apparatus of claim 58, wherein said special signature comprises a unique modulated signal associated with PSEs.

61. The apparatus of claim 58, wherein said communicator modulates an inline power signal between the first station and the second station.

62. The apparatus of claim 61, wherein said communicator utilizes current modulation.

63. The apparatus of claim 61, wherein said communicator utilizes voltage modulation.

64. The apparatus of claim 58, further comprising:

a biaser for biasing the first pair of conductors with one direct current (DC) voltage level and the second pair of conductors with a second DC voltage level, the difference between the first and second voltage level being a difference voltage; and

a modulator for modulating a signal flowing from the first pair of conductors to the second pair of conductors with a predetermined communications protocol to communicate the message from the first station to the at least one second station.

65. The apparatus of claim 64, wherein at least one of the first station and the second station is powered by the difference voltage.