Abstract:
There is provided an electrical device ( 10 ) comprising electrical elements communicating with an integral power supply ( 12 ), wherein a power connection means ( 22 ) associated with the electrical elements ( 13, 13′  and  14 ) is adapted to receive a temporary external source of electrical power such as a battery ( 24 ) to allow removal and replacement of the integral power supply without interrupting power to the electrical elements. The integral power supply ( 12 ) is adapted to receive an enduring external power source, with a second switch ( 32 ) provided to disable connection of the integral power supply ( 12 ) to the enduring power source whilst the battery ( 24 ) is connected.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to an electrical device with an internal power supply, and in particular to such electrical devices used in cable television and broadband networks. 
       BACKGROUND TO THE INVENTION 
       [0002]    Electrical devices often have integral power supplies which can be at least partially powered by an external power source, for example mains electricity in the case of a laptop computer. If the integral power supply fails, the device stops operating. This is a particular problem in cable television (CATV) and broadband networks where many active devices with integral power supplies are used, such as optical nodes, amplifiers and the like, and all signals going to and from customers subscribing to the network are routed via these devices. 
         [0003]    If the integral power supply of any one of the CATV active devices fails, the network connection and service to the subscriber also fail. The integral power supplies are typically designed with the use of electrolytic capacitors which have a low “Mean Time Between Failures” (MTBF) compared to all other components used in the active devices. Thus the integral power supply is likely to fail before other components fail. 
         [0004]    When the active device fails, there is always a signal interruption for the customer during the replacement. Analogue/digital TV, triple play Internet and video on demand services routed through the CATV network are temporarily unavailable until a technician has finished the replacement and configuration of the active device. It is very important to have a network that can be updated and configured without the customers&#39; cable service being interrupted. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with the present invention, there is provided an electrical device comprising electrical elements, such as components in a circuit, powered by an integral power supply, wherein a power connection means associated with the electrical elements is adapted to receive a temporary source of electrical power during removal and replacement of the integral power supply, the enduring external power source and the power connection means connected to a common switch means, the switch means moveable between a first position to connect the enduring external power source to the integral power supply and a second position to disconnect the integral power supply from the enduring external power source, the first and second positions being mutually exclusive and wherein the switch means is arranged to automatically switch to the second position on detecting connection of a temporary external source of electrical power to the power connection means and to revert to the first position on detecting removal of the temporary external source of electrical power, such as a battery or temporary alternating current power supply, thereby to maintain power during removal and replacement of the integral power supply. The enduring external power source may be provided by mains electricity, a generator or from coaxial cable, with such an enduring source provided for typically periods of days to years. When the integral power supply needs to be replaced, for example as is part of routine maintenance or due to failure, electrical elements requiring power can still be powered and kept operational whilst replacement of the integral power supply takes place. By having a power connection means for a temporary external power source that is typically used for periods of less than 30 minutes, a backup power source within the device does not need to be provided, so saving on space and electrical connections within the device. 
         [0006]    This enables the connection between the enduring external power supply and integral power supply to be disabled, allowing the integral power supply to be safely moved without fear of electrical shock during replacement. 
         [0007]    Typically the integral power supply will be contained within the same housing as the electrical elements. 
         [0008]    A diode means may be disposed in an electrical path between the electrical elements and the power connection means. 
         [0009]    If desired, the power connection means may be connected to one electrical element requiring power to operate, such as an amplifier unit. 
         [0010]    The integral power supply may be associated with an isolating power connector for safe removal of the integral power supply. 
         [0011]    Preferably the integral power supply and power connection means are connected to a common second switch means, the second switch means moveable between a first position to connect the electrical elements to the integral power supply and a second position to connect the electrical elements to the power connection means, the first and second positions being mutually exclusive. Thus the switch means disables the connection between the electrical elements and the integral power supply and instead substitutes a connection between the temporary power supply and electrical elements. 
         [0012]    The second switch means may be arranged to automatically switch to the second position on detecting connection of a temporary external source of electrical power to is the power connection means and to revert to the first position on detecting removal of the temporary external source of electrical power. 
         [0013]    By switching the electrical components to be powered by the temporary external supply, the integral power supply is hot swappable and can be replaced while power to the electrical elements is maintained. The device can thus remain operational during replacement of the integral power supply. 
         [0014]    The electrical device may be a device used as active outdoor CATV equipment, such as a CATV amplifier. 
     
    
     
         [0015]    The invention will now be described by way of example, and with reference to the following drawings in which: 
           [0016]      FIG. 1  is a perspective view of an amplifier in accordance with the present invention; 
           [0017]      FIGS. 2 and 3  are schematic circuit diagrams of the amplifier; 
           [0018]      FIG. 4  is an alternate embodiment of the invention; and 
           [0019]      FIG. 5  is a perspective view showing removal of an integral power supply from the amplifier. 
       
    
    
     DESCRIPTION 
       [0020]    An electrical device  10  having an internal integral power supply  12 , is shown in  FIG. 1 . The device can be any type of electrical device with an integral power supply but the example shown in  FIG. 1  is a CATV amplifier for outdoor use which includes electrical core components  13 ,  13 ′ for signal processing and amplifier unit  14  configured to amplify r.f. signals routed through the device. In this example, power supply  12  is arranged to modify an enduring external power supply, such as provided by mains electricity or coaxial cable, into suitable voltage and current characteristics for powering components within the device. The external power can be supplied through external input port  16  which supplies A.C. power at 230V to power supply  12  or through r.f. input port  18  where power at 36 to 60 VAC is taken from a coaxial cable also carrying an r.f. signal to be amplified. 
         [0021]    is The particular device shown splits and amplifies the incoming signal received at port  18  with the amplified r.f. signal transmitted through two output ports  20 . An additional external input port  22  is also provided, this additional port  22  adapted with a battery connector to receive a temporary external power source such as battery  24 . When power supply  12  needs replacing, temporary external power source  24  is connected to port  22  to ensure a continuous source of power whilst power supply  12  is replaced. This avoids failure of the device when the internal power supply  12  needs to be removed. In usual operation, electrical components  13 ,  13 ′ and  14  are powered by internal power supply  12  and housing  26  sealed shut. 
         [0022]    The electrical arrangement within device  10  is shown in schematic circuit diagrams of 
         [0023]      FIGS. 2 and 3 . Electrical paths from power supply  12  and temporary power input port  22  are routed through switch  30 , with switch  30  providing either a connection between power supply  12  and components  13 ,  13 ′ or a connection between port  22  and components  13 ,  13 ′. When power supply  12  is operational, and no temporary external power source is connected to port  22 , switch  30  occupies a normal, or rest, position as shown in  FIG. 2  ensuring electrical communication between power source  12  and the remaining components of device  10 . 
         [0024]    When power supply  12  is to be replaced, battery  24  is connected to port  22 . Switch  30  automatically detects the external power source and switches as shown in  FIG. 3  to ensure power to the electrical components is then supplied from battery  24 . Instead of battery  24 , an external alternating current power supply can be used as the temporary power source. 
         [0025]    To ensure internal power supply  12  can be safely removed, a second switch  32  is provided also responsive to connection of battery  24  at port  22  to interrupt the path between an external power supply and internal power supply  12  and switch the contacts to a neutral, or safe, position  34  or  34 ′. The external power can be provided by an enduring external power supply through port  16 , typically at 230V A.C. or can be supplied from a coaxial cable also supplying the r.f. signal to be amplified and connected to device  10  at port  18 . Both options are shown in  FIGS. 2 and 3  although it is to be understood that only one source of external power is needed for internal power supply  12 . 
         [0026]    When power supply  12  is to be replaced, an external power supply, namely battery  24 , is connected to port  22 , usually for  2  to  30  minutes, and switch  30  automatically detects the connection of the temporary external power supply  24 , operating to break the connection between internal power supply  12  and components  13 ,  13 ′ and establish an electrical connection between the temporary external supply  24  and components  13 ,  13 ′,  14  so as to maintain the power supply. 
         [0027]    On connection of temporary power supply  24 , switch  32  is also activated, switching to a neutral position  34  for an external power supply through port  16 , or position  34 ′ for an external power supply through port  18 , and interrupting the permanent external power supply to power supply  12 . 
         [0028]    The old power supply  12  is able to be safely disconnected and removed, see  FIG. 5 , without any interruption to signal processing within device  10  as power to components  13 ,  13 ′ and  14  is maintained. The device can thus remain operational even during replacement of the integral power supply. A new internal power supply is connected within housing  26 , the housing sealed once again and external battery  24  removed. Upon removal of battery  24 , switches  30 ,  32  revert to their original positions as shown in  FIG. 2  restoring the connection between integral power supply  12  and the electrical components. 
         [0029]    An alternative embodiment of the present invention is shown in  FIG. 4  where a simplified circuit is used. Battery  24  or a temporary external alternating current power supply  40 , typically between 36 to 60 VAC, are connectable via port  22  to output  23  of internal power supply  12  and so direct to analog/digital product core  13 ,  13 ′. Diode  42  is used to ensure the DC output from power supply  12  cannot travel along this alternative power input path and damage the external alternative power supply. As with  FIG. 2 , the external power can be supplied through external input port  16  which supplies A.C. power at 230V to power supply  12  or through r.f. input port  18  where power at 36 to 60 VAC is taken from a coaxial cable also carrying an r.f. signal to be amplified. Power supply  12  receives connects to an enduring external is power supply by way of an isolated power connector  44  which immediately terminates any input power to power supply  12  when power supply  12  is removed. This ensures the power supply can be safely removed and avoids the need for second switch  32  as shown in  FIG. 2 . Thus when battery  24  or power supply  40  is connected, a parallel power source is provided which avoids a power drop when power supply  12  is removed for replacement and ensures the device remains operational. If desired, the external temporary battery  24  can be connected directly to the DC output circuit of internal power supply  12 . The temporary external AC supply  40  can be connected to the amplifier circuit  14  to create a DC voltage to power up amplifier  14  together with digital core  13 ,  13 ′. 
         [0030]    By having an external power supply and switching the electrical components from the power supplied by the integral power supply to a power supplied by the temporary external supply, the integral power supply is hot swappable and can be replaced while power to the electrical elements is maintained. The present invention allows an integral power supply to be replaced whilst an amplifier or other device is in situ in the field without the active device ceasing to operate, and thus customer services being interrupted. Upon removal of the temporary power supply, the new internal power supply is automatically restored without any interruption to device functionality, so avoiding any failure of the device.