USOO6715087B1 (12) United States Patent (10) Patent No.: US 6,715,087 B1 Vergnaud et al. (45) Date of Patent: Mar. 30, 2004 (54) METHOD OF PROVIDING AREMOTE 5,506,900 A 4/1996 Fritz .......................... 379/402 POWER FEED TO A TERMINAL INA 5,530,748 A 6/1996 Ohmori ...................... 379/413 LOCAL AREA NETWORK, AND 5.991,885 A * 11/1999 Chang et al. ............... 713/300 CORRESPONDING REMOTE POWER FEED 6,175,556 B1 * 1/2001 Allen et al. - - - - - - - - - - - - - - - - - 370/293 UNIT, CONCENTRATOR, REPEATOR, AND FOREIGN PATENT DOCUMENTS TERMINAL EP O 981 227 A2 2/2000 (75) Inventors: Gérard Vergnaud, Franconville (FR); WO WO 96/23377 8/1996 Luc Attimont, Saint Germain en Laye OTHER PUBLICATIONS (FR); Jannick Bodin, Garches (FR); Raymond Gass, Bolsenheim (FR); Bearfield, J.M.: “Control the Power Interface of USB's Jean-Claude Laville, Nanterre (FR) Voltage Bus' Electronic Design, US, Penton Publishing, Cleveland, OH, vol. 45, No. 15, Jul. 27, 1997, pp. 80, 82,84, (73) Assignee: Alcatel, Paris (FR) 86 XPOOO78289 ISSN: OO13-48728. (*) Notice: Subject to any disclaimer, the term of this * cited by examiner patent is extended or adjusted under 35 Primary Examiner Dennis M. Butler U.S.C. 154(b) by 658 days. (74) Attorney, Agent, or Firm Sughrue Mion, PLLC (21) Appl. No.: 09/703,654 (57) ABSTRACT (22) Filed: Nov. 2, 2000 A method for Sending a remote power feed to a terminal in (30) Foreign Application Priority Data a local area network. Nov. 4, 1999 (FR) ............................................ 99 13834 A repeater of the local area network produces a detection Apr. 14, 2000 (FR) ............................................ OOO4834 Signal in a line to which a remote terminal is connected, and Jul. 3, 2000 (FR) ............................................ OO 08592 the Signal has an energy level that will not damage the terminal. (51) Int. Cl." ................ - - - - - - - - - - - - - - G06F 1/26 (52) U.S. Cl. ................ ... 713/300; 713/340 The presence of a remote terminal adapted to receive a (58) Field of Search ................................. 713/300, 330, remote power feed via the repeater is detected by detecting 713/340 the presence of a predetermined impedance in the terminal, and (56) References Cited power is Supplied to the terminal via the repeater in U.S. PATENT DOCUMENTS response to detection of the presence of the terminal. 4,389,694. A * 6/1983 Cornwell, Jr. ............... 361/48 5,121.482 A 6/1992 Patton ......................... 710/16 29 Claims, 13 Drawing Sheets 40 ---- U.S. Patent Mar. 30, 2004 Sheet 1 of 13 US 6,715,087 B1 RP, u-1 1 / ------- O ---- -- RPM 54 5N 2 ----- U.S. Patent Mar. 30, 2004 Sheet 2 of 13 US 6,715,087 B1 U.S. Patent Mar. 30, 2004 Sheet 3 of 13 US 6,715,087 B1 I P1 20?) ----- W - e P2 - (- w20?. 51 U.S. Patent Mar. 30, 2004 Sheet 4 of 13 US 6,715,087 B1 U.S. Patent Mar. 30, 2004 Sheet 5 of 13 US 6,715,087 B1 U.S. Patent Mar. 30, 2004 Sheet 6 of 13 US 6,715,087 B1 FG6 U.S. Patent Mar. 30, 2004 Sheet 7 of 13 US 6,715,087 B1 N | | | | | | | | 1 U.S. Patent Mar. 30, 2004 Sheet 8 of 13 US 6,715,087 B1 U.S. Patent Mar. 30, 2004 Sheet 9 of 13 US 6,715,087 B1 FIG 9 U.S. Patent Mar. 30, 2004 Sheet 10 of 13 US 6,715,087 B1 U.S. Patent Mar. 30, 2004 Sheet 11 of 13 US 6,715,087 B1 U.S. Patent US 6,715,087 B1 U.S. Patent Mar. 30, 2004 Sheet 13 of 13 US 6,715,087 B1 FIG-14 is 5 FIG-15 US 6,715,087 B1 1 2 METHOD OF PROVIDING AREMOTE disadvantage that the remote power feed unit Supplies power POWER FEED TO A TERMINAL INA to a terminal “blind”. The RJ45 connector at the end of the LOCAL AREA NETWORK, AND line L could be plugged into a terminal other than a tele CORRESPONDING REMOTE POWER FEED phone (for example a personal computer, a printer, etc.). UNIT, CONCENTRATOR, REPEATOR, AND There is a risk of damaging the electrical circuits of that TERMINAL terminal. The RJ45 connector of a terminal is generally used in the following manner: The present invention relates generally to a data process Four of the eight wires are separated into two pairs for ing local area network, for example an Ethernet network. To respectively Sending and receiving data. The terminal be more precise, the invention relates to a method of includes a transformer having one winding connected providing a remote power feed to a terminal in a data to the receive pair and a transformer having one wind processing local area network and also to a remote power ing connected to the Send pair, each of these windings feed unit, a concentrator, a repeater (also known as a hub), having a center-tap which can be connected to a ref and a terminal adapted to implement the method. erence potential via a low-resistance resistor. 15 Four other wires are not used and are grounded, often via BACKGROUND OF THE INVENTION a combination of resistors and capacitors, to eliminate FIG. 1 is a diagram showing, by way of illustrative and any crosstalk induced by the data Signals in the first non-limiting example only, an Ethernet data processing local four wires and to reduce unwanted electromagnetic area network which includes a local area network Server 1, emission. If a relatively high remote power feed a Switch 2, a repeater 3 and N terminals 4 to 4 which Voltage, for example 48 volts, is applied to that com include telephones operating in Voice over IP (VoIP) mode. bination of resistors and capacitors, or to the resistors The server 1 is connected to the Internet 0 and receives connected to the center-taps of the transformers, the packets complying with the Internet protocol (TCP/IP). The resistors can be destroyed by the current flowing in them. packets of a given call are routed via the Switch 2 and the 25 repeater 3 to a terminal Such as the telephone 4 which is OBJECTS AND SUMMARY OF THE connected to the repeater by a 8-wire line L terminated with INVENTION RJ45 connectors. The terminals connected to a data processing local area The invention therefore aims to solve this problem by network (for example personal computers, printers, etc.) are proposing a method of providing a remote power feed to a conventionally connected locally to the mains electrical terminal in a data processing local area network and Systems power supply. 110 V or 220 V power cords independent of for implementing the method which prevent all risk of the data connections are therefore used to Supply power to damage if a terminal is plugged in which is not one of the the terminals. This solution makes installation of the local terminals adapted to receive a remote power feed via the network. area network more difficult: 35 Using two cables causes problems of congestion which The invention firstly provides a method of providing a can additionally impede the free movement of perSons. remote power feed to a terminal in a local area network, the It creates electrical hazards. method entailing: In the case of a telephone, a local connection to the mains producing at least one detection Signal on at least two electrical power Supply has the additional drawback that the 40 conductors of a line for connecting the local area telephone is out of Service in the event of a mains power network to a remote terminal, that Signal having an outage, in particular in the event of a fire or natural disaster. energy Such that the terminal cannot be damaged under This is why conventional telephones receive a remote power any circumstances, feed from their local eXchange, which includes emergency detecting the presence of a remote terminal adapted to batteries. 45 receive a remote power feed by detecting the presence It is therefore desirable for Some of the terminals con of predetermined impedance in the remote terminal on nected to a data processing local area network to be provided the basis of a current created by the test Signal in that with a remote power feed via the same connection as is used line, and to send and receive data. It is also desirable to be able to Sending a power Supply current in that line when the install the remote power feed unit anywhere on the line L 50 presence of a terminal adapted to receive a remote (either inside or outside a repeater 3), to enable easy addition power feed is detected. to an existing network. The above method prevents all risk to the terminals One way of transmitting a remote power feed current is to because the remote power feed current is Sent only if the use two of the eight wires of the line L: four other wires form terminal has been identified as one which is adapted to two pairs of wires respectively used to transmit and to 55 receive a remote power feed. The intensity and duration of receive data. Another method, referred to as a phantom the detection signal are chosen So that the operation of circuit, connects the two terminals of a power Supply gen detecting the terminal cannot cause any damage if the erator in the remote power feed unit to respective center-taps terminal is not one which is adapted to receive a remote of a winding of a transformer connected to the pair for power feed.