Electrical computers and digital processing systems: support – Computer power control – By external command
Reexamination Certificate
1999-11-08
2003-03-18
Lee, Thomas (Department: 2185)
Electrical computers and digital processing systems: support
Computer power control
By external command
C370S410000, C710S015000
Reexamination Certificate
active
06535983
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to Ethernet applications and more particularly to providing a signal connection and power connection to a device via a hub and Ethernet twisted pair wiring.
BACKGROUND OF THE INVENTION
Network devices typically communicate via wired data lines and receive power from a separate line. For example, personal computers (“PCs”) may communicate Ethernet signals via category three (CAT-3) or category five (CAT-5) twisted pair wire and receive power from a second cable connected to a power source, such as a wall socket or a battery. However, it is desirable to be able to eliminate the need for the second cable.
Plain old telephone service (“POTS”) combines a voice signal with a power signal. The combined signal is transmitted over twisted pair cable between the telephone and the line card at the public telephone exchange office. The line card also supplies power over the two wires carrying the voice signal. However, the voice signal supported by POTS is not sufficient for bandwidth intensive communications needs, such as, Ethernet communications. Similarly, ISDN communications transmit power and digital data between an ISDN modem and a telephone switch. However, ISDN data rates are more than an order of magnitude lower than Ethernet data rates.
Providing power to an end device (computer, Ethernet phone, peripheral device, etc.) using the Ethernet twisted pair wiring is desirable in many situations. Providing power locally (powering an end device at its location) presents problems for Ethernet applications. One example of a problem encountered is the security camera problem wherein the local supply of power can be problematic as to the secure status of such a security camera. A possible solution is to provide the transmission medium as a medium for supplying power (the Ethernet wire is used for supplying power). However, this involves some problems as well.
Wireless network adapters can interconnect PCs, or other networked device. The wireless network adaptors use, for example, infrared (IR) or radio frequency (RF) modulation to transmit data between wireless access points and the wireless adaptors connected to PCs. Although the wireless adaptors and wireless access points may be more expensive than comparable wired equipment, they provide savings in wiring costs and permit greater flexibility by allowing the PCs to be moved to any location within the range of the system without the necessity of rewiring the building.
Typically, a transceiver (meaning transmitter and receiver) called a wireless access point, mounted at an elevated location, such as on a ceiling or high on a wall, provides network data communications between a network hub, switch, router or server, to all the PCs located in that room which are equipped with a compatible wireless networking adaptor. The wireless access point is an active electronic device that requires a communications link to a hub or server as well as electrical power to operate. Both the data signal and power signal must be provided to the wireless access point. The data signal is typically at a lower voltage than the power signal, but at a significantly higher frequency, sufficient to sustain a high data transfer rate (e.g., 100 kilobits per second or higher). The available power is usually 110V or 220V AC at frequencies below one hundred Hz. Often two separate sets of wires are used to carry the data signal and power signal. One set of wires is used to couple the wireless access point and the hub and the other set of wires is used to couple the wireless access point to the power outlet.
Eliminating the need for separate power and data wiring simplifies the installation of a wireless access point and can reduce the cost of the installation. Therefore, it is desirable to transmit sufficient electrical power to operate the wireless access point through the network cable that is used to connect the wireless access point to the hub or server.
One possible solution is to transmit power on the unused wires of the data cable. An example of this approach can be found in the VIPSLAN-IOTM product manufactured by the JVC Information Products Company of Irvine, Calif. Of course this requires that additional, unused wire pairs be available in the data cable, which may not always be available. Also, if a change in the networking standard in the future dictates the use of the currently unused wire pairs in the networking cable, this solution becomes difficult to implement.
Therefore, what is needed is a solution that reduces the wiring requirements to transmit data and power to a wireless access point without having to use additional wire pairs.
At this time, the IEEE 802.3 standard (Ethernet) does not address power issues. One possibility for supplying power is to provide the power on the Ethernet connection, namely the transmission medium. The issues as to supplying power involve issues as to the environment of the system as well as in the overall costs.
Typically in Ethernet environments power is applied locally at a hub or concentrator and this unit distributes power to various network devices which are connected to slots of the hub or concentrator. However this approach does not take into account problems involving unusual environments or needs to have the network device at a distant location from the hub. The standard does not provide for hubs which supply power to other devices, the IEEE 802.3 working group is attempting to develop a standard that addresses this, but it is not in the standard yet.
Another network device which has been increasingly used in network environments is a network phone. Such a phone device converts audio analog signals into digital signals and sends the digital signals out in the form of packets over a network such as a local area network (LAN). The phone devices can be provided with a power circuit which is integrated into the phone. The AC power is applied to the phone and the power is conditioned (e.g. rectified) and possibly also converted by a transformer. The use of such discrete power supplies, one power supply associated with each telephone unit, provides an expense and further complication to such telephone systems.
A changeover from the approach of supplying power locally to a system involving supplying power via the network wires involves various problems including the need to condition the power supplied over the wire. One significant problem is the need to supply the power over the network wires at a relatively high voltage level. For example, the use of 45 volts dc over the wire is considered to be advantageous. However, the use of high voltage levels results in higher cost with regard to semiconductor devices used in the network device. Typically, voltage levels below 30 volts are desirable with regard to maintaining semiconductor unit costs at a low level. Semiconductor devices which use higher voltage levels typically result in higher costs.
Besides the issues as to supplying power, any effort to add functionality to existing Ethernet standards must be compatible with existing equipment compliant with IEEE 802.3 (relating to carrier sense multiple access (CSMA) local area network applications). Current termination practices in the industry place a passive resistor is a very low wattage ({fraction (1/10)} W) between signal pairs that are targeted for power insertion. If power is blindly applied to the Ethernet cable, it would damage equipment that uses the passive resistor termination. In the alternative, the power must be limited to less than {fraction (1/10)} W (this is impractical). It therefore is significantly important that a safe and effective method of signaling and detecting the need for power, of a particular end device, be provided for powering the Ethernet cable.
SUMMARY AND OBJECTS OF THE INVENTION
It is an object of the invention to provide an Ethernet system with a hub having an associated power source for selectively supplying system power over Ethernet twisted pair wiring to end devices and for detecting the indication of the system power need an
Dryer Paul Francis
McCormack Michael S.
Stapleton Nicholas Mark
3Com Corporation
Lee Thomas
McGlew and Tuttle , P.C.
Suryawanshi Suresh K
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