Combined handset and pots filter

Abstract

The present invention is generally directed to a telephone handset for testing the transmission quality of a local loop. In accordance with one aspect of the invention, the telephone handset includes a connector configured to connect to the local loop at, for example, a junction box. The invention also includes a low-pass filter circuit electrically interposed between the connector and operational circuitry of the telephone handset. In operation, the low-pass filter is designed to pass (substantially undisturbed) electrical signals within the POTS frequency band from the connector to the operational circuitry. In the same way, the low-pass filter is designed to substantially block the passage of electrical signals above the POTS frequency range. In this way, the low-pass filter blocks the introduction of high frequency signals, which may otherwise generate intermodulation products within the audible range, from reaching the operational circuitry of the testing handset. In accordance with another feature of one embodiment of the invention, a device is provided for detecting the presence of xDSL signals on a local loop. In accordance with this embodiment, at least one band-pass or high-pass filter is added in parallel with the low-pass filter. The output of the at least one band-pass or high-pass filter is then analyzed to determine whether an xDSL signal is present within that frequency band (defined by the at least one band-pass or high-pass filter).

What is claimed is:  
     
         1 . A device for testing the transmission quality of a local loop comprising: 
 a connector configured to connect to the local loop;    a low-pass filter circuit electrically connected to the connector and interposed between the connector and operational circuitry of the device, the low-pass filter being designed to pass substantially undisturbed electrical signals within the POTS frequency band from the connector to the operational circuitry, the low-pass filter being designed to substantially block the passage of electrical signals above the POTS frequency range.    
     
     
         2 . The device as defined in    claim 1   , wherein the device is a testing handset.  
     
     
         3 . The device as defined in    claim 1   , wherein the device is a transmission impairment measurement system.  
     
     
         4 . The device as defined in    claim 1   , wherein low-pass filter circuit is defined by a cutoff frequency ranging from approximately 3.4 kilohertz to approximately 10 kilohertz.  
     
     
         5 . The device as defined in    claim 1   , further including means for bypassing the low-pass filter.  
     
     
         6 . The device as defined in    claim 5   , wherein the means for bypassing includes a manually-operated switch means.  
     
     
         7 . The device as defined in    claim 6   , wherein the manually-operated switch means includes a double-pole double-throw switch.  
     
     
         8 . The device as defined in    claim 5   , wherein the mean for bypassing includes an automatically-operated switch means, responsive to means for sensing a high frequency signal component, wherein the high frequency signal component is in an xDSL frequency band.  
     
     
         9 . The device as defined in    claim 1   , wherein the low-pass filter is designed to have an input impedance of approximately 600 ohms.  
     
     
         10 . The device as defined in    claim 1   , wherein the low-pass filter is designed to have an input impedance of approximately 900 ohms.  
     
     
         11 . The device as defined in    claim 1   , wherein the low-pass filter is a passive filter.  
     
     
         12 . The device as defined in    claim 11   , wherein the low-pass filter is designed exclusively from inductors and capacitors.  
     
     
         13 . The device as defined in    claim 1   , wherein the low-pass filter is an active filter.  
     
     
         14 . A device for testing a phone line, the improvement comprising: 
 a low-pass filter circuit electrically interposed between a handset connector and operational circuitry of the handset, the low-pass filter designed to pass substantially undisturbed electrical signals within the POTS frequency band from the connector to the operational circuitry, the low-pass filter being designed to substantially block the passage of electrical signals above the POTS frequency range.    
     
     
         15 . An improved telephone for use in a system carrying both POTS and xDSL signal transmissions, comprising: 
 operational circuitry designed to provide and support operational functions of the telephone;    an input/output connector for communicating signals in a POTS frequency band between a local loop and the operational circuitry;    a low-pass filter circuit;    means for detecting the presence of an xDSL signal; and    switching means, responsive to the means for detecting, for selectively interposing the low-pass filter circuit between the input/output connector and the operational circuitry of the telephone handset, whereby the switching means switches in the low-pass filter when an xDSL signal is present.    
     
     
         16 . The telephone as defined in    claim 15   , wherein low-pass filter circuit is defined by a cutoff frequency ranging from approximately 3.4 kilohertz to approximately 10 kilohertz.  
     
     
         17 . The telephone as defined in    claim 15   , wherein the switching means includes a manually-operated switch means.  
     
     
         18 . The telephone as defined in    claim 17   , wherein the manually-operated switch means includes a double-pole double-throw switch.  
     
     
         19 . The telephone as defined in    claim 15   , wherein the switching mean includes an automatically-operated switch means, responsive to means for sensing a high frequency signal component, wherein the high frequency signal component is in an xDSL frequency band.  
     
     
         20 . The telephone as defined in    claim 15   , wherein the low-pass filter is designed to have an input impedance of approximately 600 ohms.  
     
     
         21 . The telephone as defined in    claim 15   , wherein the low-pass filter is designed to have an input impedance of approximately 900 ohms.  
     
     
         22 . The telephone as defined in    claim 15   , wherein the low-pass filter is a passive filter.  
     
     
         23 . The telephone as defined in    claim 22   , wherein the low-pass filter is designed exclusively from inductors and capacitors.  
     
     
         24 . The telephone as defined in    claim 15   , wherein the low-pass filter is an active filter.  
     
     
         25 . An improved telephone for use in a system carrying both POTS and xDSL signal transmissions, comprising: 
 operational circuitry designed to provide and support operational functions of the telephone;    an input/output connector for communicating signals in a POTS frequency band between a local loop and the operational circuitry;    a plurality of low-pass filter circuits disposed for selective interconnection between the input/output connector and the operational circuitry; and    switching means electrically connected to the input/output connector, each of the plurality of low-pass filter circuits, and the operational circuitry, the switching means adapted to selectively interconnect one of the plurality of low-pass filter circuits between the input/output connector and the operational circuitry.    
     
     
         26 . The telephone as defined in    claim 25   , wherein the switching means includes a double-pole double-throw switch.  
     
     
         27 . The telephone as defined in    claim 25   , wherein the switching means includes a multi-position double-pole rotary switch.  
     
     
         28 . A device for detecting the presence of an xDSL signal on a local loop comprising: 
 an input electrically connected to the local loop;    a first filter electrically connected to the input for passing signals within a POTS frequency band;    a second filter electrically connected to the input for passing signals having frequency components above the POTS frequency band, the second filter defined by a high input impedance so that POTS signals passing through the first filter are substantially undisturbed;    a signal detector electrically connected to an output of the second filter for detecting the presence of a signal having a frequency above the POTS frequency band; and    signaling means responsive to the signal detector for signaling that a signal having a frequency above the POTS frequency band has been detected.    
     
     
         29 . The device as defined in    claim 28   , wherein the second filter is a high-pass filter.  
     
     
         30 . The device as defined in    claim 28   , wherein the second filter is a band-pass filter.  
     
     
         31 . The device as defined in    claim 28   , further including a plurality of second filters, each defining differing frequency bands.  
     
     
         32 . The device as defined in    claim 28   , wherein the signal detector is a circuit defined to detect the presence of a predetermined amount of energy within a frequency band, the predetermined amount of energy indicative of the presence of a signal within that frequency band.  
     
     
         33 . The device as defined in    claim 28   , wherein the signal detector includes a circuit for computing a Fourier Transform of the signal output from the second filter.  
     
     
         34 . The device as defined in    claim 28   , wherein the signaling means produces a visual indicator.  
     
     
         35 . The device as defined in    claim 34   , wherein the signaling means includes at least one LED.  
     
     
         36 . The device as defined in    claim 28   , wherein the signaling means produces an audible output.