Abstract:
A POTS splitter of the present invention generally include a telephone line interface, a data receiver interface that is connected to the telephone line interface, and a low pass filter that is connected to the telephone line interface. The low pass filter operates to pass only those frequencies that are lower than 4 Khz. And, the entire configuration of a single line POTS splitter is maintainable upon a circuit board that is no greater than 2.0 inches by 1.5 inches, with a maximum depth of 0.630 inches. The POTS splitter is operational in the temperature range of −40° to +70° C.

Description:
CLAIM TO PRIORITY  
       [0001]    The present application claims priority to U.S. provisional application having serial No. 60/184,082, filed Feb. 22, 2000, and entitled “Signal Splitter”. The identified provisional patent application is hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to POTS (plain old telephone service) systems that carry both voice and data transmissions and, more particularly, to a device for splitting the frequency of the POTS system to separate or split a transmission into their respective voice and data components.  
         BACKGROUND OF THE INVENTION  
         [0003]    The plain old telephone service, or POTS, is the service that delivers analog voice signals to a user&#39;s home or office. These analog voice signals are generally transmitted at a frequency of less than 4 kHz. The same twisted pair of wires that carry the analog voice signals are also capable of carrying digital signals albeit at higher frequencies than the analog voice signals, e.g., 4 kHz to 1.1 MHz. To enable operation of both POTS and a digital subscriber line (xDSL) a splitter is used to divide or split the analog and digital signals.  
           [0004]    Depending on the type of DSL a splitter may be required at both a remote location, i.e., the customer premise, and at the central office (CO) location. For example, with asymmetric DSL, or ADSL, both are required. In this instance, the remote POTS splitter splits the incoming telephone signal into a low frequency signal for voice devices by utilizing a low pass filter and into a high frequency data signal for computers. Meanwhile, the CO POTS splitter splits its incoming signal into a low frequency voice signal for the public switched telephone network (PSTN) by utilizing a low pass filter and into a high frequency signal for a DSL access multiplexor to direct the signal to the internet.  
           [0005]    To make voice and xDSL widely available to the general public there is a need for the POTS splitters at both the central office and at the customer premise be cost-effective, of a minimally intrusive size, easily installed, as well as durable and reliable over a range of temperatures.  
         SUMMARY OF THE INVENTION  
         [0006]    The needs described above are in large measure met by the POTS splitter of the present invention. The POTS splitter generally include a telephone line interface, a data receiver interface that is connected to the telephone line interface, and a low pass filter that is connected to the telephone line interface. The low pass filter operates to pass only those frequencies that are lower than 4 Khz. And, the entire configuration of a single line POTS splitter is maintainable upon a circuit board that is no greater than 2.0 inches by 1.5 inches, with a maximum depth of 0.630 inches. The POTS splitter is operational in the temperature range of −40° to +70° C.  
           [0007]    The low pass filter is composed of a minimal number of components, i.e. a common mode choke, a first mutual inductor, a second mutual inductor, an inductor, a first capacitor and a second capacitor. In the instance that the POTS splitter is a central office (CO) POTS splitter, rather than a remote POTS splitter, a pair of DC blocking capacitors are placed between the telephone line and the data receiver. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a block diagram of a remote POTS splitter of the present invention.  
         [0009]    [0009]FIG. 2 is a block diagram of a central office (CO) POTS splitter of the present invention.  
         [0010]    [0010]FIG. 3 is a circuit diagram of the remote POTS splitter of the present invention.  
         [0011]    [0011]FIGS. 4A and 4B provide a view of the remote POTS splitter of FIG. 3 with the actual components mounted on a circuit board.  
         [0012]    [0012]FIG. 5 is a circuit diagram of the CO POTS splitter of the present invention.  
         [0013]    [0013]FIG. 6 is a front view of a line card incorporating a plurality of the CO POTS splitters of FIG. 5.  
         [0014]    [0014]FIG. 7 is a side view of the line card of FIG. 6.  
         [0015]    [0015]FIG. 8 is provides a front view of a multiple slot chassis for accepting a plurality of the line cards of FIGS. 6 and 7. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    A remote POTS splitter and central office (CO) POTS splitter of the present invention operate to divide a telephone signal into signals of different frequencies. The splitters perform this operation through the use of a filter whose number of components are limited and whose operation is reliable through a range of temperatures.  
         [0017]    Referring to FIG. 1 a block diagram of the remote POTS splitter  20  of the present invention is provided. As shown, an incoming telephone line  22  is provided at remote POTS splitter  20  and is tapped to provide the high frequency xDSL signal to a data receiver  24 , e.g., xDSL modem. Line  22  is also directed to a low pass filter  26  whereby the high frequency xDSL signal is filtered out allowing only the low frequency voice signal to pass to the user&#39;s voice device  28 .  
         [0018]    Referring to FIG. 2 a block diagram of the central office (CO) POTS splitter  60  of the present invention is provided. As shown an incoming line  62  from a user&#39;s premise is provided at CO POTS splitter  60  and is tapped to provide the high frequency xDSL signal to a data receiver  64 , e.g., DSL access multiplexor or modem. However, prior to passing the high frequency signal to data receiver  64 , the signal is passed through a pair of DC blocking capacitors, C 3  and C 4 . Line  62  is also directed to low pass filter  66  whereby the high frequency xDSL signal is filtered out allowing only the low frequency voice signal to pass to the public switched telephone network (PSTN)  66 .  
         [0019]    The purpose of low pass filters  26  and  66  is two-fold. First, for xDSL signals, protection from the high frequency transients and impedance effects that occur during POTS operation—ringing transients, ring trip transients, and off-hook transients and impedance changes—is provided. For POTS voice band service, the low pass filters provide protection from xDSL signals which may impact through non-linear or other effects remote devices (handset, fax, voice band modem, etc.) and central office operation.  
         [0020]    Referring to FIG. 3, a circuit diagram of remote POTS splitter  20  is provided. As shown, line  22  enters splitter  20  and is tapped to provide the high frequency signal to xDSL data receiver  24  without intervention of additional circuitry. Line  22  is also provided to low pass filter  26  where xDSL frequencies are filter out. As shown, filter  26  includes a common-mode choke, CM Choke, which is used to eliminate noise on line  22 . Filter  26  further includes a mutual inductor L1 that is preferably in the configuration of an RM-6 core, which is connected to the series combination of capacitor C 1  and inductor L3. A second mutual inductor L2 that is preferably in the configuration of an RM-6 core is connected between the series combination and a capacitor C 2 .  
                       TABLE 1                       Component   Preferred Embodiment   Alternative Embodiment                   CM Choke   835 uH per inductor   835 uH per inductor       L1   6.8 mH per inductor   6.0 mH per inductor       C1   0.056 uF   0.047 uF       L3   434 uH   590 uH       L2   6.8 mH per inductor   6.0 mH per inductor       C2   0.033 uF   0.027 uF                  
 
         [0021]    Of course, other component values may be used without departing from the spirit or scope of the invention.  
         [0022]    The preferred embodiment of filter  26  preferably utilizes magnetic materials exhibiting a 2000 permeability, with the CM choke using a core of higher permeability. When utilizing the specified magnetic material and the component values listed in Table 1, the preferred embodiment of filter  26  and resulting POTS splitter  20  meets with ANSI specification T1E1.4/98-007R5 Annex E, the contents of which is hereby incorporated by reference. The use of lower permeability materials and tight tolerances on final inductance allows this embodiment of POTS splitter  20  to work properly across a full range of temperatures from −40° C. to +70° C.  
         [0023]    The alternative embodiment of filter  26  preferably uses magnetic materials exhibiting a 2000 permeability (L1, L2, L3), CM choke utilizing a higher permeability, to achieve the proper operational characteristics and compliance with ANSI specification T1E1.4/98-007R5 Annex E.  
         [0024]    Specifically, each embodiment of POTS splitter  20  meets the following electrical specifications:  
         [0025]    1. Open Circuit Inductance: 51.7 mH-58.5 mH 1.2 KHz 100 mV (across line  22  short).  
         [0026]    2. Interwinding Capacitance: 100 nF MAX. 25 Hz 100 mV.  
         [0027]    3. DC Resistance: 8.45-9.34 Ohms 0.250 Ohms MAX difference between tip and ring of line  22 .  
         [0028]    4. High Voltage Test: 275 VDC (tip to ring).  
         [0029]    5. −600-900 Ohm Test: &lt;−1.0 dB @ 1 KHz.  
         [0030]    3 dB attenuation @ 7.5 KHz ±1.25 KHz  
         [0031]    50 dB attenuation min. @ 21 KHz  
         [0032]    ±1.5 dB Max. from 200 Hz-3.4 KHz with respect to 1 KHz  
         [0033]    ±2.0 dB max. from 3.4 KHz-4.0 KHz with respect to 1 KHz.  
         [0034]    6. −600-100 Ohm Test: 65 dB attenuation min. from 26.5 KHz-300 KHz  
         [0035]    55 dB attenuation min. from 300 KHz-1.2 MHz.  
         [0036]    72 dB attenuation min. from 35 KHz-75 KHz.  
         [0037]    Remote POTS splitter  20  may be provided with terminals or flying leads for connection to line  22 , data receiver  24  and voice device  28 . Alternatively, remote POTS splitter  20  may be provided with RJ-11 interfaces for quick installation by a professional or user. In either instance, remote POTS splitter  20  may be mounted indoors or outdoors within a housing.  
         [0038]    [0038]FIG. 4A provides a view of remote POTS splitter  20  as mounted atop a circuit board  30  wherein terminals  32  are provided. This view of remote POTS splitter  20  shows the compact nature of the splitter (approximately 1.325 inches by 1.0625 inches) and the reduced number of components necessary to implement its operation. FIG. 4B provides a view of remote POTS splitter  20  wherein RJ-11 interfaces  34  are provided, the size of circuit board  30  having been slightly increased (2.0 inches by 1.0625 inches). In each configuration the overall depth of POTS splitter is approximately 0.630 inches.  
         [0039]    Referring to FIG. 5 a circuit diagram of CO POTS splitter  60  is provided. As can be seen, CO POTS splitter  60  is identical to remote POTS splitter  20  with the exception that DC blocking capacitors C 3  and C 4  have been added between line  62  xDSL data receiver  64 . Capacitors C 3  and C 4  are each preferably 0.12 uF. Filter  66  component values, operation, and electrical specifications are identical to those provided above in with respect to filter  26 .  
         [0040]    [0040]FIGS. 6 and 7 provide a view of a plurality of CO POTS splitters  60  mounted atop a circuit board  70  that is provided as a line card  72 . In this preferred embodiment, eight CO POTS splitters  60  are mounted atop board  70  which is additionally provided with gold interface terminals  74 . Once again, the compact nature of splitter  60  can be appreciated as eight CO POTS splitters are able to occupy a line card  72  that is only 4.5 inches by 8.0 inches, with an overall maximum circuit depth of 0.630 inches.  
         [0041]    [0041]FIG. 8 provides a front view of a multiple slot chassis  76  for accepting a plurality of the line cards  72 , whereby the line cards  72  interface with a mother board connector  78 .  
         [0042]    The present invention may be embodied in other specific forms without departing from the spirit of the essential attributes thereof; therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.