Method and apparatus for remote powering of device connected to network

• US 6,762,675 B1
• Filed: 09/27/1999
• Issued: 07/13/2004
• Est. Priority Date: 09/27/1999
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Edsall, Thomas, Cafiero, Luca, De Nicolo, Maurilio, Nakamura, Karl, Hang, Soei-Shin
• Primary Examiner(s): Zimmerman, Brian
• Assistant Examiner(s): YANG, CLARA I
• Application Number:
  US09/406,248
• Time in Patent Office: 1,751 Days
• Field of Search: 340/10.42, 340/310.01, 340/825.52, 340/505, 340/524, 340/310.02, 340/310.06, 340/310.07, 340/568.1, 340/568.4, 340/571, 340/572.1, 340/568.2, 340/3.51, 340/333, 340/310.08, 340/310.03, 340/310.04, 340/310.05, 340/10.34, 340/425.2, 713/200, 713/300, 710/62, 710/8, 455/522, 379/22.01, 379/93.36
• US Class Current: 340/10.42
• CPC Class Codes: G06F 1/266 Arrangements to supply power to external peripherals either directly from the computer or under computer control, e.g. supply of power through the communication port, computer controlled power-strips
• CPC Class Codes: H04L 12/10 Current supply arrangements
• CPC Class Codes: H04L 49/30 Peripheral units, e.g. input or output ports
• CPC Class Codes: H04L 49/40 Constructional details, e.g. power supply, mechanical construction or backplane
• CPC Class Codes: H04M 3/18 with means for reducing interference or noise; with means for reducing effects due to line faults with means for protecting lines
• CPC Class Codes: H04M 7/006 Networks other than PSTN/ISDN providing telephone service, e.g. Voice over Internet Protocol (VoIP) , including next generation networks with a packet-switched transport layer H04L65/00 takes precedence; aspects not specific to the type of network H04M3/00; special services in those networks H04M3/42

Abstract

A network node determines the suitability of coupled devices for being remotely line powered before actually powering them. The node scan its ports to determine which ports are coupled to devices. The node then interrogates the coupled devices. A unique discovery tone or bit pattern is generated and sent to devices coupled to ports. The node then monitors the port for a return signal. If there is a return signal, it is compared to the transmitted discovery signal. The signal will be identical after allowing for line losses if the coupled device is suitable for remote line powering. If the comparison yields a match, the network node supplies remote line power to the device.

Claims

1. A method for remote line powering a network node comprising:

receiving a discovery signal at a network device;

relaying a return signal back to the network node corresponding to the discovery signal when the network device is configured for remote line powering and is not powered;

sending no corresponding return signal when the network device is not configured for remote line powering whether that device is powered or unpowered;

receiving remote power from the network node after sending the corresponding return signal; and

automatically switching from a discovery signal loopback relay position to a remote line powering position when receiving remote power.

2. The method of claim 1 including receiving multiple discovery signal retries before receiving power from the network node if the return signal matches the discovery signal.

3. The method of claim 1 including receiving at least one initialization packet after receiving power from the network node.

4. The method of claim 3 including sending an identification packet responsive to the received initialization packet and receiving power from the network node responsive to data in the identification packet.

5. A network endpoint for connecting to a network cable comprising:

a receive input for connecting to the network cable;

a transmit output for connecting to the network cable; and

a switching circuit having a first position relaying a discovery packet received on the receive input back out through the transmit output and automatically switching to a second position receiving data and remote power at the input and outputting data and providing a power return path at the output.

6. A network endpoint according to claim 5 wherein the switching circuit includes an output power interface outputting the remote power received at the receive input to a phone.

7. The network endpoint according to claim 6 including a transformer circuit coupled between the receive input and the output power interface.

8. The network endpoint according to claim 6 including a network device interface including a power connection and signaling connections.

9. The network endpoint according to claim 8 wherein the network device interface includes a differential pair of receive lines, a differential pair of transmit signals and power signals.

10. The network endpoint according to claim 5 wherein the switching circuit includes an interface outputting the data and the remote power to a phone.

11. An article comprising a machine-accessible medium having associated data that, when accessed, results in a machine determining suitability of providing remote power to a network device, the machine-accessible medium comprising:

code for generating a discovery signal before the network device receives power;

code for transmitting the discovery signal from the network node to the network device;

code for monitoring for a return signal from the network device;

code for comparing the return signal to the discovery signal if the return signal is received from the network device;

code for determining that the network device is suitable for remote powering when the return signal matches the discovery signal; and

code for determining that the network device is unsuitable for remote powering when the return signal is not received or when the return signal, with the exception of line losses, does not match the discovery signal.

12. The article according to claim 11 wherein the code for determining that the network device is suitable for remote powering further comprises code for outputting a power signal from the network node for powering the network device when the network device loops back the discovery signal.

13. The article of claim 11 wherein the code for determining suitability of providing remote power to a network device further comprises code for waiting for the network node to become idle before transmitting the discovery signal.

14. The article of claim 11 wherein the code for determining suitability of providing remote power to a network device further comprises:

code for interrogating a first port on the network node for a connection to a first network device;

code for transmitting the discovery signal and monitoring for the matching return signal on the first port when the first network device is connected to the first port;

code for interrogating a second port on the network node for a connection to a second network device;

code for transmitting the discovery signal and monitoring for the matching return signal on the second port when the second network device is connected to the second port;

code for powering the first network device remotely with the network node when the matching return signal is detected on the first port;

code for powering the second network device remotely with the network node when the matching return signal is detected on the second port; and

code for detecting disconnected devices and unpowering the port before another device is attached.

15. A circuit, comprising:

a first interface;

a second interface; and

a switching circuit having a first state for receiving a remote power discovery signal on the first interface and sending a reply signal out through the second interface and automatically switching to a second state for receiving data and remote power at the first interface and outputting data and providing a power return path at the second interface.

16. A circuit according to claim 15 wherein the first interface includes receive terminals and the second interface includes transmit terminals.

17. The circuit according to claim 15 wherein the switching circuit includes a first switch and a second switch configured in the first switching circuit state to couple a first receive terminal on the first interface to a first transmit terminal on the second interface and configured in the second switching circuit state to couple the first receive terminal on the first interface and the first transmit terminal on the second interface to phone interface terminals.

18. The circuit according to claim 17 wherein the switching circuit includes a third switch and a fourth switch configured in the first switching circuit state to couple a second receive terminal on the first interface to a second transmit terminal on the second interface and configured in the second switching circuit state to couple the second receive terminal on the first interface and the second transmit terminal on the second interface to phone interface terminals.

19. The circuit according to claim 15 including a power circuit coupled between the first and second interface and the switching circuit.

20. The circuit according to claim 19 including taps on the power circuit for supplying power to an Internet phone.

21. The circuit according to claim 19 wherein the power circuit includes a first transformer coupled between the first interface and the switching circuit and a second transformer coupled between the second interface and the switching circuit.

22. The circuit according to claim 15 wherein the switching circuit automatically switches from the first state to the second state when power is received across the first and second interface.

23. The circuit according to claim 15 wherein the first interface includes a differential pair of receive signal contacts and the second interface includes a differential pair of transmit signal contacts.

24. The circuit according to claim 15 wherein the switching circuit when in a non-powered condition receives the discovery signal at the first interface and passes the discovery signal to the second interface.

25. A device, comprising

a circuit configured to loop back signals on a network interface to indicate a remote power capability and further configured to change from looping back signals to connecting signals on the network interface to an endpoint interface when remote power is detected at the network interface.

26. The device according to claim 25 including an output power interface for connecting to power received at the network interface.

27. The device according to claim 26 including a transformer circuit coupled between the network interface and the output power interface.

28. The device according to claim 25 wherein the endpoint interface is configured to connect to a Voice over Internet Protocol (VoIP) phone.

29. The device according to claim 25 wherein the circuit loop backs signals when no power is applied to the circuit.

30. The device according to claim 25 wherein the network interface includes a differential pair of receive contacts and a differential pair of transmit contacts.