Abstract:
Vehicles such as airliners or trains can be equipped with a form of local area network in which individual network connections are made to individual passenger seats using standard telephony connectors. Passengers having computers can connect to the network using their own conventional telephone cables. Wireless communications technology is used to link the vehicle network to external ground stations or satellite systems. To meet the DC power requirements of mobile computer users, the vehicle includes a DC power source. A normally unused wire-pair in the telephony connectors brings the DC power to each seatback. A slightly modified connector is used to transfer the DC power to the computer&#39;s DC power subsystem.

Description:
FIELD OF THE INVENTION 
   The present invention relates to computers and more particularly to an alternate power source for modem-capable, ordinarily-mobile computers. 
   BACKGROUND OF THE INVENTION 
   Early personal computers were desktop systems which were so heavy and so bulky that it was assumed they would be left in place once installed. However, the benefits of a transportable personal computer were recognized early on and considerable efforts have been made to develop lighter and more portable computers. The advent of new technologies has permitted the development of newer, smaller and lighter personal computers which are known by various names, such as notebook computers, laptop computers or even palmtop computers, depending on their relative size. Personal computers are now light enough and small enough that they can be carried as hand luggage and can be used almost anywhere, including the confines of most airline seats. Computers of this type are referred to generically as mobile computers in the following specification. 
   Some users, having acquired a mobile computer small enough and light enough to carry on an airplane, want to be able to use that computer for the duration of even long flights either in a standalone mode and/or to stay “in touch” with others. Some airlines are considering accommodating such users by installing what amounts to a local area network (LAN) in some of their airplanes. At least a limited number of the seats in the airplane would be connected to the LAN through standard telephone connections, including a standard telephone jack such as the RJ45 jack widely used throughout the United States and in some other countries. The LAN would include a server or base station which could be used to establish radio communications with ground-based stations or satellite systems. An authorized mobile computer user would access the LAN simply by plugging his modem telephone cable into an RJ45 jack located in an armrest or in the seatback or bulkhead ahead of him or her. 
   While the existence of an airplane LAN and the ability to connect to that LAN through standard telephony connections at an airplane seat will enable a mobile computer user to stay “in touch” with the outside world, that user will remain “in touch” only until his or her computer battery becomes discharged. 
   Even with the best battery technology currently available, it is not possible to operate most mobile computers for extended periods of time on battery power alone. Experienced travelers have attempted to avoid the problems of exhausted batteries by carrying spare batteries or even using the AC power outlet found in some airplane lavatories. Neither of these solutions is particularly appealing. Spare batteries are heavy and hard to install, particularly in the limited seating space available in most airplanes. An airplane lavatory is certainly not an ergonomically sound working environment and, in any event, is available on an extended basis only to a traveler who is willing to be totally indifferent to the discomfort of his or her fellow travelers. 
   SUMMARY OF THE INVENTION 
   The present invention is an alternate power source for a modem-capable computer that can meet the needs of a computer-using traveler during long flights (or long ground vehicle trips) provided the vehicle is one of the type including a data network using standard telephony connectors for data distribution to users. The alternate power source is for use with any computer having a DC power subsystem and a modem which can be connected to such a data network through a multi-wire telephone connector having at least one available pair of wires. The alternate power source includes a pair of electrical leads which are connected at one end to the available pair of wires and which are coupled at the other end to an electrical interface to the DC power subsystem of the computer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, details of preferred embodiments of the invention may be more readily ascertained from the following detailed description when read in conjunction with the accompanying drawings wherein: 
       FIG. 1  is a simplified representation of a portion of vehicle interior, such as an airplane, including an internal network and wireless communications capabilities; 
       FIG. 2  is a similar representation of the same vehicle interior modified to support use of the present invention; 
       FIG. 3  is a block diagram of a conventional computer system showing conventional external connections both to an external data network and to an external AC power source; 
       FIG. 4  is a simplified representation of a conventional telephone connector such as the widely used RJ45 telephone connector; 
       FIG. 5  is a simplified representation of an RJ45 telephone connector modified to implement the present invention; 
       FIG. 6  represents one embodiment for an electrical interface between a modified RJ45 telephone connector and the DC power subsystem of a computer; and 
       FIG. 7  represents an alternate embodiment for an electrical interface between a modified RJ45 telephone connector and the DC power subsystem of a computer. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1  is intended to show a portion of a vehicle interior. For the sake of convenience, the vehicle will be referred to as an airliner although it could be any kind of air, land or water vehicle equipped with the elements described below. Two passenger seats  10  and  12  are shown. The passenger seats are conventional to the extent they include fold-down tray tables, such as tray table  14 , which passengers can use for food service and to support books, papers or even a mobile computer, such as mobile computer  16 . 
   The passenger seats are unconventional in that they are equipped with wires  24  leading to a network switch  18  located in a non-passenger area of the airliner. Network switch  18  is itself connected to a wireless transceiver  20  which can both send data to and receive data from ground stations (not shown) or satellites (also not shown) linked to terrestrial data networks. In a preferred type of implementation, a shared, media  22  is used to interconnect the individual seatback wires  24  to the network switch  18 , although direct connections between each seat and the network switch are well within the scope of the present invention. 
   To make the system useful to as many travelers as possible, standard telephony connections are employed at each seatback since a standard modem-capable mobile computer is routinely equipped with a standard telephone cable which can be used to complete a data connection between a standard telephone jack on the mobile computer and a standard telephone wall jack leading to a private or public switched telephone network. In the illustrated environment, the seatback jack takes the place of a wall jack and the network switch takes the place of the switched telephone network. 
   While the described environment can satisfy a traveler&#39;s desire to get “in touch” with others during even long airline flights, the traveler nevertheless can stay in touch only so long as his mobile computer battery (or batteries) retain a sufficient charge. 
   Referring to  FIG. 2 , to eliminate the dependence of the traveler on battery power, the present invention requires that the described environment be modified by including a low voltage (12 volts or less) DC power source  28  in the airliner. As will be described in more detail below, the DC power source  28  can be used to provide DC power to mobile computer users through a media  30  and individual seatback connections  32 . Many of the elements shown in  FIG. 2  are substantially unchanged from the form they have in the  FIG. 1  environment, which is indicated by the use of primes with certain of the reference numbers. The media  30  and seatback connections  32  are designated by new reference numbers to indicate that they perform new functions in the  FIG. 2  environment. 
     FIG. 3  is a block diagram of a standard mobile computer  34  which can be used in implementing the present invention. The computer is conventional in that it includes a central processor  36 , memory elements  38 , input/output (I/O) adapters  40  and a DC power subsystem  42 . While a conventional desktop system usually includes a three-prong jack for receiving a grounded 110 volt power plug, a mobile system usually has a removable DC power plug  44  connected to an AC adapter  46 . Typically, the DC power provided by the AC adapter  46  is used both to power the mobile computer system and to restore the charge on a rechargeable battery (not shown) within the DC power subsystem  42 . 
   It is common to include a modem  48  in a mobile computer either as an integral permanent component or in the form of a pluggable component such a modem complying with the requirements of a known standard such as the PCMCIA standard. Most modems, whether fixed or pluggable, are terminated externally using a standard telephony connector  50  such as the ubiquitous RJ45 telephone jack. 
     FIG. 4  is a simplified representation of a standard RJ45 telephone connector, having a jack  52  can receive a complementary plug  54  which terminates conventional telephone twisted pair (TP) wires. It should be noted that the drawing is only a logical representation of an RJ45 connector, not a physical representation. An actual RJ45 connector is a much more complex physical structure than the structure illustrated. A standard telephony connector includes four pairs of electrical contacts. A one line telephone or standard single modem connection is connected using wires terminating at only one of the three pairs, usually the wire pair (1-2) in the plug. It is standard practice to designate the wire pair connections as “tip” and “ring” leads to identify telephony functions which are performed by signals carried on the leads. Where a two line telephone or a second telephone phone is to be installed, a second conductor (and wire) pair (usually 3-6) is used. The third and fourth conductor pairs are rarely used for any purpose. Many conventional telephone cables don&#39;t even include wires connected to the third and fourth conductor pairs. In the environment illustrated in  FIG. 1 , it is likely that only a third conductor/wire pair (4-5) would be used to establish a data connection to an in-vehicle network switch. 
   The present invention capitalizes on the fact that the wire pair (4-5) in a standard RJ45 connector is rarely used. The invention appropriates that wire pair to provide an electrical connection between the DC power source  28  and a plug  56 . A complementary jack  58  includes a conventional wire pair (1-2) connection to an internal or pluggable modem  60 , but also includes an unconventional wire pair (4-5) connection. This wire pair is used to carry DC power to the computer&#39;s DC power subsystem. The amount of DC power that can be transported over telephone twisted pair wiring is great enough to supply the power needs of the mobile computer system and may be sufficient to trickle-charge the computer&#39;s battery even while the computer is in active use. 
     FIG. 6  depicts a first specific embodiment of the invention. In that Figure, the network connection and the DC power source are represented generically as a signal/power source  66 . In this embodiment, the wire-pair 4-5 is connected directly to the DC power subsystem  64  of the computer. This embodiment assumes, of course, that the computer was initially designed to support such a direct connection. 
     FIG. 7  depicts a second specific embodiment which would permit the invention to be used with currently available mobile computers. In the second embodiment, the plug to be inserted into the computer telephone jack is modified to carry a pair of electrical leads which are terminated in a DC power plug  68  of the type already commonly found on mobile computers. DC power would be transferred to the computer&#39;s DC power subsystem  64  using the DC power plug  68  and a complementary jack  70  in exactly the same way those components are normally used to transfer power provided by an AC adapter. The advantage of this embodiment is that no changes are required within the computer itself in order to make use of the invention. 
   While there have been described what are considered to be preferred embodiments of the present invention, variations and modifications in the preferred embodiments will occur to those skilled in the art once they are made aware of the invention. As just one example, the invention could readily be used with telephony connectors other than the standard RJ45 connector. Therefore, it is intended that the appended claims shall be construed to include not only the preferred embodiments but all such variations and modifications that fall within the true spirit and scope of the invention.