Digital access arrangement circuitry and method for connecting to phone lines having a DC holding circuit with programmable current limiting

• US 7,515,672 B2
• Filed: 10/03/2003
• Issued: 04/07/2009
• Est. Priority Date: 04/22/1997
• Status: Expired due to Fees

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Sooch, Navdeep S., Scott, Jeffrey W., Welland, David R., Tuttle, George Tyson, Dupuis, Timothy J.
• Primary Examiner(s): Ghayour; Mohammad H
• Assistant Examiner(s): Malek; Leila
• Application Number:
  US10/679,013
• Publication Number:
  US 20050100104A1
• Time in Patent Office: 2,013 Days
• Field of Search: 375/257, 375/220, 375/377, 375/285, 379/350, 379/412, 379/90.01, 379/399.01
• US Class Current: 375/377
• CPC Class Codes: H04L 25/0266 Arrangements for providing Galvanic isolation, e.g. by means of magnetic or capacitive coupling
• CPC Class Codes: H04L 25/06 Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
• CPC Class Codes: H04L 7/033 using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
• CPC Class Codes: H04M 11/06 Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
• CPC Class Codes: H04M 19/001 Current supply source at the exchanger providing current to substations
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A digital direct access arrangement (DAA) circuitry may be used to terminate the telephone connections at the user'"'"'s end that provides a communication path for signals to and from the phone lines. Briefly described, the DAA provides a programmable circuit for the DC termination for a variety of international phone standards. The invention may also be utilized with circuitry for transmitting and receiving a signal across a capacitive isolation barrier. More particularly, a DC holding circuit is provided in which a programmable DC current limiting mode is available. In the current limiting mode, power may be dissipated in devices external to a DAA integrated circuit. Moreover, much of the power may be dissipated in external passive devices, such as resistors.

Claims

1. A communication system, comprising:

phone line side circuitry configured for coupling to phone lines;

powered side circuitry configured for coupling to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements; and

a DC holding circuit within the phone line side circuitry, the DC holding circuit being programmable in response to data transmitted across the isolation barrier to operate the DC holding circuit in a plurality of modes, the DC holding circuit operates in at least a first mode to meet a first phone line interface standard and a second mode to meet a second phone line interface standard, the second phone line interface standard having a DC current limit requirement;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements; and

wherein the powered side circuitry and the phone line side circuitry are configured so that power is provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards.

2. The communication system of claim 1, the DC holding circuit comprising a phone line side integrated circuit and at least one external device, the external device dissipating more power in the second mode than in the first mode.

3. The communication system of claim 2, wherein a substantial portion of the power dissipated by the DC holding circuit in the second mode is dissipated external to the phone line side integrated circuit.

4. The communication system of claim 3, wherein 50% or more of the power dissipated by the DC holding circuit is dissipated external to the phone line side integrated circuit.

5. The communication system of claim 1, further comprising the isolation barrier coupled between the phone line side circuitry and the powered side circuitry.

6. The communication system of claim 1, wherein the powered side circuitry is further configured to provide the clock signal to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

7. The communication system of claim 1, wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

8. The communication system of claim 1, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

9. The communication system of claim 1, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

10. A communication system, comprising:

phone line side circuitry configured for coupling to phone lines;

powered side circuitry configured for coupling to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements; and

a DC holding circuit within the phone line side circuitry, the DC holding circuit being programmable in response to data transmitted across the isolation barrier to operate the DC holding circuit in a plurality of modes, the DC holding circuit operates in at least a first mode to meet a first phone line interface standard and a second mode to meet a second phone line interface standard, the second phone line interface standard having a DC current limit requirement;

wherein said powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein said phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements that is separate from the first isolation capacitor and the second isolation capacitor;

wherein the powered side circuitry and the phone line side circuitry are configured so that power is provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards; and

wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

11. The communication system of claim 10, the DC holding circuit comprising a phone line side integrated circuit and at least one external device, the external device dissipating more power in the second mode than in the first mode.

12. The communication system of claim 11, wherein a substantial portion of the power dissipated by the DC holding circuit in the second mode is dissipated external to the phone line side integrated circuit.

13. The communication system of claim 12, wherein 50% or more of the power dissipated by the DC holding circuit is dissipated external to the phone line side integrated circuit.

14. The communication system of claim 10, further comprising the isolation barrier coupled between the phone line side circuitry and the powered side circuitry.

15. The communication system of claim 10, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

16. The communication system of claim 10, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

17. A method of providing a communication system configured for coupling to a phone line, comprising:

coupling an isolation barrier between powered side circuitry and phone line side circuitry, the isolation baffler comprising a plurality of isolation elements;

configuring the powered side circuitry to communicate a first digital differential signal to at least two of the isolation baffler elements, the at least two isolation baffler elements comprising at least a first isolation capacitor and a second isolation capacitor;

configuring the phone line side circuitry to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

configuring the powered side circuitry to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements;

configuring the powered side circuitry and the phone line side circuitry so that power is provided from the phone line side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards;

forming a DC holding circuit within the phone line side circuitry, the DC holding circuit comprising a phone line side integrated circuit and external circuitry external to the integrated circuit;

providing a programmable circuit for switching the DC holding circuit between at least a first and second mode of operation, the first mode of operation for at least a first phone line interface standard and the second mode of operation for at least a second phone line interface standard, the second standard having a DC termination current limit; and

coupling the internal circuitry and external circuitry so that if the DC holding circuit is operated in the second mode of operation more power may be dissipated in the external circuitry during the second mode of operation than during the first mode of operation.

18. The method of claim 17, further comprising dissipating more power during the second mode of operation in the external circuitry than in the internal circuitry.

19. The method of claim 17, wherein the clock signal is provided from the powered side circuitry to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

20. The method of claim 17, wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

21. The method of claim 17, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

22. The method of claim 17, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

23. A method of providing a communication system configured for coupling to a phone line, comprising:

coupling an isolation barrier between powered side circuitry and phone line side circuitry, the isolation barrier comprising a plurality of isolation elements;

configuring the powered side circuitry to communicate a first digital differential signal to at least two of the isolation barrier elements, the at least two isolation barrier elements comprising at least a first isolation capacitor and a second isolation capacitor;

configuring the phone line side circuitry to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals, wherein at least one of the first digital differential signal and the second digital differential signal includes both data and control information;

configuring the powered side circuitry to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements, wherein the clock signal is provided from the powered side circuitry to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor;

configuring the powered side circuitry and the phone line side circuitry so that power is provided from the phone line side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards;

forming a DC holding circuit within the phone line side circuitry, the DC holding circuit comprising a phone line side integrated circuit and external circuitry external to the integrated circuit;

providing a programmable circuit for switching the DC holding circuit between at least a first and second mode of operation, the first mode of operation for at least a first phone line interface standard and the second mode of operation for at least a second phone line interface standard, the second standard having a DC termination current limit; and

coupling the internal circuitry and external circuitry so that if the DC holding circuit is operated in the second mode of operation more power may be dissipated in the external circuitry during the second mode of operation than during the first mode of operation.

24. The method of claim 23, further comprising dissipating more power during the second mode of operation in the external circuitry than in the internal circuitry.

25. The method of claim 23, wherein each of said plurality of isolation elements of said isolation baffler comprises a capacitor.

26. The method of claim 23, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

27. A communication system, comprising:

phone line side circuitry configured for coupling to phone lines;

powered side circuitry configured for coupling to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements;

a DC holding circuit within the phone line side circuitry for reducing power dissipation requirements of an integrated circuit within the communication system, the DC holding circuit comprising;

at least one switchable circuit, the switchable circuit having a first state for a non-current limiting mode of operation and a second state for a current limiting mode of operation,

external circuitry external to the integrated circuit, and

internal circuitry within the integrated circuit, the external circuitry and the internal circuitry being coupled together wherein the external circuitry dissipates more power in the current limiting mode than in the non-current limiting mode;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements; and

wherein the powered side circuitry and the phone line side circuitry are configured so that power is provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards.

28. The communication system of claim 27, the external circuitry comprising at least one power dissipation resistor.

29. The communication system of claim 27, wherein when the switchable circuit is in the second state, the external circuitry dissipates more power than the internal circuitry.

30. The communication system of claim 29, wherein when the switchable circuit is in the second state, one or more resistors in the external dissipate more power than the internal circuitry.

31. The communication system of claim 27, wherein the powered side circuitry is further configured to provide the clock signal to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

32. The communication system of claim 27, wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

33. The communication system of claim 27, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

34. The communication system of claim 27, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

35. A communication system comprising:

phone line side circuitry configured for coupling to phone lines;

powered side circuitry configured for coupling to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements;

a DC holding circuit within the phone line side circuitry for reducing power dissipation requirements of an integrated circuit within the communication system, the DC holding circuit comprising;

at least one switchable circuit, the switchable circuit having a first state for a non-current limiting mode of operation and a second state for a current limiting mode of operation,

external circuitry external to the integrated circuit, and

internal circuitry within the integrated circuit, the external circuitry and the internal circuitry being coupled together wherein the external circuitry dissipates more power in the current limiting mode than in the non-current limiting mode;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements that is separate from the first isolation capacitor and the second isolation capacitor;

wherein the powered side circuitry and the phone line side circuitry are configured so that power is provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards; and

wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

36. The communication system of claim 35, the external circuitry comprising at least one power dissipation resistor.

37. The communication system of claim 35, wherein when the switchable circuit is in the second state, the external circuitry dissipates more power than the internal circuitry.

38. The communication system of claim 37, wherein when the switchable circuit is in the second state, one or more resistors in the external circuitry dissipate more power than the internal circuitry.

39. The communication system of claim 35, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

40. The communication system of claim 35, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

41. A communication system comprising:

phone line side circuitry configured for coupling to phone lines;

powered side circuitry configured for coupling to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements;

a DC holding circuit compatible with a phone line standard having current limit requirements for reducing power dissipation requirements of an integrated circuit within the communication system, the DC holding circuit comprising;

external circuitry external to the integrated circuit, and

internal circuitry within the integrated circuit, the external circuitry and the internal circuitry being coupled together wherein the external circuitry dissipates more power than the internal circuitry in at least one mode of operation;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry of the communication system is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements; and

wherein the powered side circuitry and the phone line side circuitry are configured so that power is provided from the powered side circuitry of the communication system to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards.

42. The communication system of claim 41, the external circuitry comprising at least one power dissipation resistor.

43. The communication system of claim 41, wherein one or more resistors in the external circuitry dissipate more power than the internal circuitry in at least one mode of operation.

44. The communication system of claim 41, wherein the powered side circuitry is further configured to provide the clock signal to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

45. The communication system of claim 41, wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

46. The communication system of claim 41, wherein each of said plurality of isolation elements of said isolation baffler comprises a capacitor.

47. The communication system of claim 41, wherein at least a portion of said plurality of isolation elements of said isolation baffler each comprises a capacitor.

48. A communication system comprising:

phone line side circuitry configured for coupling to phone lines;

powered side circuitry configured for coupling to the phone line side circuitry through an isolation baffler comprised of a plurality of isolation elements;

a DC holding circuit compatible with a phone line standard having current limit requirements for reducing power dissipation requirements of an integrated circuit within the communication system, the DC holding circuit comprising;

external circuitry external to the integrated circuit, and

internal circuitry within the integrated circuit, the external circuitry and the internal circuitry being coupled together wherein the external circuitry dissipates more power than the internal circuitry in at least one mode of operation;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements that is separate from the first isolation capacitor and the second isolation capacitor;

wherein the powered side circuitry and the phone line side circuitry are configured so that power is provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards and

wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

49. The communication system of claim 48, the external circuitry comprising at least one power dissipation resistor.

50. The communication system of claim 48, wherein one or more resistors in the external circuitry dissipate more power than the internal circuitry in at least one mode of operation.

51. The communication system of claim 48, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

52. The communication system of claim 48, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

53. A method of providing a communication system configured for coupling to a phone line, comprising:

coupling an isolation barrier between powered side circuitry and phone line side circuitry, the isolation barrier comprising a plurality of isolation elements;

configuring the powered side circuitry to communicate a first digital differential signal to at least two of the isolation barrier elements, the at least two isolation barrier elements comprising at least a first isolation capacitor and a second isolation capacitor;

configuring the phone line side circuitry to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

configuring the powered side circuitry to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements;

configuring the powered side circuitry and the phone line side circuitry so that power is provided from the phone line side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards;

forming a DC holding circuit within the phone line side circuitry, the DC holding circuit being formed with internal circuitry internal to an integrated circuit and external circuitry external to the integrated circuit, the DC holding circuit compatible with at least one phone line interface standard having a DC current limit requirement; and

coupling the internal circuitry and external circuitry so that more power is dissipated in the external circuitry than in the internal circuitry.

54. The method of claim 53, wherein the clock signal is provided from the powered side circuitry to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

55. The method of claim 53, wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

56. The method of claim 53, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

57. The method of claim 53, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

58. A method of providing a communication system configured for coupling to a phone line, comprising:

coupling an isolation barrier between powered side circuitry and phone line side circuitry, the isolation barrier comprising a plurality of isolation elements;

configuring the powered side circuitry to communicate a first digital differential signal to at least two of the isolation barrier elements, the at least two isolation barrier elements comprising at least a first isolation capacitor and a second isolation capacitor;

configuring the phone line side circuitry to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals, wherein at least one of the first digital differential signal and the second digital differential signal includes both data and control information;

configuring the powered side circuitry to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements, wherein the clock signal is provided from the powered side circuitry to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor;

configuring the powered side circuitry and the phone line side circuitry so that power is provided from the phone line side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards;

forming a DC holding circuit within the phone line side circuitry, the DC holding circuit being formed with internal circuitry internal to an integrated circuit and external circuitry external to the integrated circuit, the DC holding circuit compatible with at least one phone line interface standard having a DC current limit requirement; and

coupling the internal circuitry and external circuitry so that more power is dissipated in the external circuitry than in the internal circuitry.

59. The method of claim 58, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

60. The method of claim 58, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

61. A method of operating a communication system configured for coupling to a phone line, comprising:

providing phone line side circuitry configured for coupling to phone lines;

providing powered side circuitry configured for coupling to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements;

providing integrated circuitry and nonintegrated circuitry to comprise a DC holding circuit within the phone line side circuitry;

coupling the integrated circuitry and the non-integrated circuitry; and

dissipating more power in the external circuitry than in the internal circuitry if the DC holding circuit is utilized for a phone line interface standard having a DC current limit requirement;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements; and

wherein the powered side circuitry and the phone line side circuitry are configured so that power is provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards.

62. The method of claim 61, wherein the powered side circuitry is further configured to provide the clock signal to the phone line side circuitry through an isolation element that is separate from the first isolation capacitor and the second isolation capacitor.

63. The method of claim 61, wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

64. The method of claim 61, wherein each of said plurality of isolation elements of said isolation baffler comprises a capacitor.

65. The method of claim 61, wherein at least a portion of said plurality of isolation elements of said isolation barrier each comprises a capacitor.

66. A method of operating a communication system configured for coupling to a phone line, comprising:

providing phone line side circuitry configured for coupling to phone lines;

providing powered side circuitry configured for coupling to the phone line side circuitry through an isolation barrier comprised of a plurality of isolation elements;

providing integrated circuitry and nonintegrated circuitry to comprise a DC holding circuit within the phone line side circuitry;

coupling the integrated circuitry and the non-integrated circuitry; and

dissipating more power in the external circuitry than in the internal circuitry if the DC holding circuit is utilized for a phone line interface standard having a DC current limit requirement;

wherein the powered side circuitry is configured to communicate a first digital differential signal to at least two of the plurality of isolation elements, the at least two isolation elements comprising at least a first isolation capacitor and a second isolation capacitor;

wherein the phone line side circuitry is configured to communicate a second digital differential signal to the first isolation capacitor and the second isolation capacitor so that the first and second digital differential signals are communicated across the same first and second isolation capacitors and so that the first and second isolation capacitors bidirectionally transfer the first and second digital differential signals;

wherein the powered side circuitry is further configured to provide a clock signal to the phone line side circuitry through at least one of the plurality of isolation elements that is separate from the first isolation capacitor and the second isolation capacitor;

wherein the powered side circuitry and the phone line side circuitry are configured so that power is provided from the powered side circuitry to the phone line side circuitry while still maintaining the isolation required by the phone line isolation regulatory standards; and

wherein at least one of the first digital differential signal and the second digital differential signal includes both data information and control information.

67. The method of claim 66, wherein each of said plurality of isolation elements of said isolation barrier comprises a capacitor.

68. The method of claim 66, wherein at least a portion of said plurality of isolation elements of said isolation baffler each comprises a capacitor.