Abstract:
A voice over DSL telephone system for a customer premises. The system includes a network interface device having a DSL filter coupling DSL service from a central office to the customer premises wiring and a switch for automatically connecting POTS service from the central office to the customer premises wiring whenever there is no active integrated access device, IAD, connected to the wiring. A detection circuit detects the presence or absence of the IAD and opens and closes the switch accordingly. Both DSL and POTS ports of an IAD may then be connected to the same customer premises wiring. Telephone sets are coupled to the customer premises wiring through low pass filters which block DSL frequencies.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     REFERENCE TO A MICROFICHE APPENDIX 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to customer premises telecommunications systems and more particularly to a system which uses existing customer premises wiring for both POTS and DSL services without interference with local exchange carrier POTS service. 
     The common telephone service provided to customer premises, including homes and businesses, is analog service provided over copper wires usually referred to as twisted pair. This service is referred to as POTS, or plain old telephone system, service. It is sometimes considered to be synonymous with the public switched telephone network, PSTN. Most of the PSTN now carries signals digitally. However, POTS service from the local exchange carrier, LEC, central office, CO, to customer premises is analog and carried over copper wire. In addition to voice, the tip and ring signals and power to operate telephone sets in the customer premises are carried over the copper wires. An advantage of this system is that the telephone system does not depend on having power available at the customer premises. The CO normally uses standard grid power to operate and has emergency power backup systems which keep the telephone system operating in emergency situations. 
     Digital subscriber loops or lines, DSL, were developed to provide digital data service over the same twisted pair lines which are used for POTS. This type of service has great advantage when customers connect computers to the Internet or other networks from their homes or small business premises. Both POTS service and DSL service can be provided over the same copper wires so that no additional expense of running extra lines for DSL is required. POTS service operates at frequencies below 4 KHz while DSL operates at frequencies above 4 KHz up to several MHz. It is therefore a simple matter to separate the signals by frequency filters. 
     As the DSL service has become more available, it is becoming common to provide voice over DSL, VoDSL, service. In this type of service, the analog telephones in a customer premises are connected to a device, e.g. a VoDSL Integrated Access Device (IAD), which converts the analog telephone signals to digital signals and sends them to the CO over a DSL connection. An example of an IAD is the CPE, customer premises equipment, described in U.S. Pat. No. 6,272,209 issued on Aug. 7, 2001. This arrangement has a number of advantages. For example, a number of separate telephone voice signals can be transmitted simultaneously over one DSL connection. Data signals may also be transmitted over the DSL connection at the same time. There is no need to run additional twisted pairs when a customer wants additional telephones or additional computer connections. This arrangement effectively extends the PSTN digital system past the CO and into the customer premises. 
     VoDSL systems must have a source of electrical power. It has not proven practical to provide power from the CO as is done for POTS service. The power requirements are too great. As a result, the systems use power from the customer premises. For emergency purposes, the systems may have batteries for backup when the AC power is lost. However, such systems must be maintained by the customer to be sure that the backup batteries are charged and are replaced at regular intervals. In any case, backup batteries have a limited amount of power available and will run down after a long outage of AC power. 
     As VoDSL systems become more common, more customers want to perform their own installation. This requires that the system be easy and simple to install. Such systems should be designed to plug into existing wiring to the extent possible. Running new wiring in a customer premises requires a major effort which most customers would not want to undertake. It is also desirable that an IAD be located close to a customer&#39;s personal computer, since they often have a network connection directly to the computer. However, in existing systems IADs must be connected between the copper wires entering the premises and the internal wires connected to the telephone sets. This normally requires breaking or interrupting the wiring at or near a location on the exterior of the customer premises. The analog signals between the IAD and the telephone sets in the customer premises must be isolated from the POTS service connection to the CO. 
     It would be desirable to have a voice over DSL system which is simple to install, does not require additional wiring in the customer premises and which provides telephone service when the VoDSL system loses power. 
     SUMMARY OF THE INVENTION 
     A voice over DSL system according to the present invention includes an improved network interface device, conventional customer premises wiring, and an integrated access device having both DSL and POTS ports coupled to the customer premises wiring. The improved network interface device includes a filter which couples DSL frequencies across the network interface device at all times and an automatic switch which opens when an integrated access device is operating to isolate POTS service in the customer premises from POTS service in a local exchange carrier central office. 
     In one embodiment, the invention includes a DSL blocking filter between a telephone set and its connection to the customer premises telephone wiring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of prior art interconnection of voice over DSL service from a local exchange carrier to a customer premises telecommunications system. 
     FIG. 2 is a block diagram of the interconnection of voice over DSL service from a local exchange carrier to a customer premises telecommunications system according to the present invention. 
     FIG. 3 is schematic diagram of a network interface device according to the present invention. 
     FIG. 4 is a block diagram of the interconnection of an integrated access device connection to telephone wiring carrying both POTS and DSL signals. 
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     With reference to FIG. 1, there is illustrated a conventional or prior art system for providing VoDSL service to a customer premises indicated by the dotted line box  10 . A local exchange carrier, LEC, central office, CO,  12  contains the equipment for providing both POTS service and DSL service. These services may be connected to the customer premises  10  over a pair of copper wires  14 . The wires  14  are terminated at a network interface device, NID,  16  which is normally located on an outer surface, e.g. wall, of the customer premises  10 . The NID  16  normally identifies the point of demarcation between telephone company owned equipment and customer owned equipment inside the premises  10 . 
     The NID  16  couples the signals from wires  14  to telephone wiring  18  and  20  within the premises  10 . In a system having only POTS service, the wiring  18  and  20  may be directly connected as indicated by dotted lines  22 . 
     An integrated access device, IAD,  24  has a DSL port  26  connected by wires  28  to the telephone wiring  18  leading from the NID  16 . IAD  24  has a POTS port  30  connected by wiring  32  to the telephone wiring  20 . IAD  24  may also have a network port  34  connected by wiring  36  to a computer  38 . The IAD  24  is connected to standard AC power through a power cord  40 . A number of conventional telephone sets  42  are connected to the telephone wiring  20 . An example of an integrated access device which provides both VoDSL service and network connections for computers is described in co-pending U.S. Pat. No. 6,272,558, entitled “Multi-Services Communications Device,” issued Aug. 7, 2001, which is incorporated by reference herein in its entirety. 
     In the system of FIG. 1, the DSL service from CO  12  is connected through wiring  14 ,  18  and  28  and through NID  16  to the DSL port  26  of IAD  24 . The IAD  24  converts high frequency digital signals at port  26  to low frequency analog POTS signals at port  30 . The IAD also provides all of the power, tip and ring, etc. signals required for POTS service at port  30 . These POTS signals are coupled through wiring  32  and  20  to the telephone sets  42  which function in the same manner as if the POTS signals came from the CO  12 . 
     As indicated above, the telephone wiring  18  and  20  can be directly connected if only POTS service is provided to the residence  10 . During construction of a residence, the telephone wiring is normally run from the location of NID  16  to most of the rooms in the residence. The local exchange carrier will normally install the NID  16  on the exterior of the residence  10  and make a connection to the wiring  18 . When the owner of the premises requests DSL service, the telephone wiring  18  must be cut close to the NID to isolate the wiring  20  from the POTS service from the CO  12  as indicated by dashed lines  22 . If the IAD can be located near the NID  16 , then wiring  28  and  32  can be fairly short. But, quite often the interior premises location corresponding to the exterior location of NID  16  is not a desirable location for the IAD  24 . For example, the NID is often placed outside a garage which would not provide appropriate temperature and humidity conditions. If the NID is outside of most other rooms in the house, the owner does not want the IAD mounted on the interior wall for aesthetic reasons. In addition, a network cable  36  is often required to be run from the IAD  24  to a computer  38 . The usual compromise is to place the IAD near the computer  38 , since it may look like another piece of computer equipment, and then run two long pairs of wires  28  and  32  to intercept the incoming telephone wiring  18  near the NID  16 . 
     With reference to FIG. 2, a system for providing VoDSL service to the premises  10  according to the present invention is illustrated. In FIG. 2 the LEC CO  12  and wiring  14  may be the same as in FIG.  1 . An improved NID  50  is mounted on an exterior wall of premises  10 . The NID is connected to telephone wiring  52 , preferably preinstalled, in the premises  10 . The wiring  52  is normally run to and accessible in each living and work area of the premises  10 . Telephone sets  54  are coupled to the wiring  54 , preferably through DSL blocking low pass filters  56 . Filters  56  may be commercially available devices such as Model FIL-0002-AB sold by 2WIRE, Inc. or equivalent devices. 
     An IAD  58  may be located anywhere in premises  10  and is connected by a standard telephone plug set  60  to the same wiring  52  as the telephone sets  54 . IAD  58  may have a network connection  62  to a computer  64 . The IAD  58  may be connected to wiring  52  at any accessible point in the premises  10 , i.e. essentially anywhere in the premises  10  and no extra wiring is needed to connect near the NID  50 . Thus, it is convenient to locate IAD  58  near computer  62  and simply plug cable  60  into a nearby telephone jack just like plugging in telephones  54 . 
     In FIG. 3, there is provided a schematic diagram of an embodiment of an improved NID  50 . As shown in FIG. 2, the NID  50  couples signals from the telephone company wiring  14  to the on premises telephone wiring  52 . A high pass filter or DSL pass filter  66  is connected between wiring  14  and wiring  52 . Filter  66  blocks POTS voltages and signals, but allows DSL frequency signals to pass from wiring  14  to wiring  52  at all times. 
     The NID  50  also provides a switched connection of wiring  14  and wiring  52  through a relay  68 . Relay  68  includes a pair of normally closed contacts  70  and  72 , driven by a relay coil  74 . When no current flows through coil  74 , the contacts  70  and  72  close and couple all signals, including DC voltage and current between wiring  14  and wiring  52 . 
     When the contacts  70 ,  72  are closed, the CO  12  can provide POTS service to telephone sets in premises  10 . However, this would cause a conflict if an IAD  58  is connected to wiring  52  and is powered up. The NID  50  therefore includes an IAD detector  76  for sensing the presence of an active, i.e. powered up, IAD  58  connected to wiring  52 . In this embodiment, the detector is connected in line between switch  70  and one side of on premises wiring  52 . It provides an output  78  to drive the coil  74  of relay  68 . When the detector  76  detects the presence of an active IAD  58 , it drives current through coil  74  to open contacts  70  and  72  and disconnect POTS service from the LEC CO  12 . When the IAD  58  loses power or otherwise fails to provide POTS service, the detector  76  stops driving current through coil  74  so that switches  70  and  72  close and POTS service from CO  12  is reconnected. 
     There are a number of ways in which the detector  76  may detect the presence of an active IAD  58 . In one embodiment, detector  76  may sense the flow of DC current from wiring  14  to wiring  52  which occurs if the CO  12  is providing POTS service to telephone sets  54  and no active IAD is connected to wiring  52 . If IAD  58  begins providing the DC voltages needed for POTS service, the DC current from CO  12  through detector  76  should drop essentially to zero. When that occurs, the current sensing circuit uses the IAD POTS voltage on lines  52  to drive current through coil  74  causing contacts  70  and  72  to open and stop the POTS connection to CO  12 . If the IAD  58  fails when contacts  70  and  72  are open, the current through coil  74  will stop and the contacts  70  and  72  will return to their normally closed position, restoring POTS service from CO  12 . 
     It will also be apparent that other means may be used to determine whether IAD  58  is active. For example a voltage detector may be used instead of a current detector. It would also be possible to have a dedicated signal line from IAD to detector  76 . To avoid running extra wires for such dedicated signal line, the IAD  58  could generate a signal, e.g. a fixed frequency tone, on lines  52  when it is active and the detector  76  could detect the signal and switch relay  68  in response. Depending on the type of detection circuitry used, the IAD detector may be connected to standard AC power through a power cord, not shown, and may include a backup battery. 
     This operation of the NID  50  also permits installation of the IAD by the owner of the premises without wiring changes. The NID  50  may be installed when no VoDSL service is supplied to the premises  10 . Since the NID  50  is located outside the premises  10 , it may be installed without entering the premises and without changing the on premises wiring. With the NID  50  in place, the rest of the system can be installed by plugging cables into standard sockets. The IAD  58  may be plugged into any available telephone jack with a standard connector cable. DSL filters may be installed for each telephone set by unplugging the telephone from its jack and inserting an inline filter such as the one described above. 
     As shown in FIG. 2, the IAD  58  is connected to the standard in house wiring  52  for both DSL and POTS service. Since these two services operate at different frequencies, it is a simple matter to make one connection to the IAD and separate the signals internally. 
     FIG. 4 provides a simple filter arrangement which allows IAD  24  of FIG. 1 to be used in the FIG. 2 embodiment. IAD  24  has separate DSL port  26  and POTS port  30 . In FIG. 4, a high pass filter  90  is connected to DSL port  26 . A low pass filter  92  is connected to POTS port  30 . The two filters  90 ,  92  are connected to a single pair of wires  94 , which may be connected to the in house wiring  52 . The filter  90  allows DSL signals to pass between wires  94  and DSL port  26 , but blocks POTS signals. The filter  92  allows POTS signals to pass between wires  94  and POTS port  30 , but blocks DSL signals. 
     This arrangement illustrates how the present invention allows the IAD  58  to be located essentially anywhere in premises  10  without modifying the originally installed telephone wiring. The IAD  58  may exchange DSL signals with the CO  12  over the in house wiring  52 . It may simultaneously communicate with the telephones sets  54  in POTS service which operates in a different frequency band. As noted above, it is preferred to use DSL blocking, i.e. low pass, filters  56  for each telephone set  54 . The in house wiring  52  serves as a common bus for both frequency bands. 
     While the present invention has been illustrated and described in terms of particular apparatus and methods of use, it is apparent that equivalent parts may be substituted of those shown and other changes can be made within the scope of the present invention as defined by the appended claims.