Abstract:
Consumer process equipment (CPE) for cost effective caller identification (CID) and call-waiting (CW) for a multi-line telephone includes a single CIDCW detection circuit and a single switch for coupling the single CIDCW detection circuit between a plurality of telephone lines. The CPE is able to process CIDCW information over a plurality of telephone lines by dynamically switching the single switch from one telephone line to another, depending upon the current state of the CPE.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to customer premises equipment (CPE) (e.g. a telephone base and receiver unit) for use in telephone subscriber systems and more particularly to a customer premises equipment for use in telephone subscriber systems having caller identification (CID) and call waiting (CW) on a plurality of telephone lines.  
           [0003]    2. Background Information  
           [0004]    The call-waiting (CW) feature is generally well-known and available on many telephone systems (i.e., central offices). In conventional CW, when a subscriber to the CW service is engaged in a telephone conversation with a second party, the central office notifies the subscriber when a third party is attempting to call the subscriber. Typically, the central office notifies the subscriber of the incoming third party call by providing a CW tone or “click” which is audible to the subscriber. The subscriber then has the option to place the second party on hold and speak to the third party, or to ignore the CW signal and continue speaking to the second party.  
           [0005]    Another service offered on some central offices is caller identification (CID). In the conventional CID feature the central office transmits a digitally encoded signal, representing the telephone number of a calling party, to a subscriber&#39;s customer premises equipment (CPE) (e.g., a telephone base and receiver unit). Provided that the subscriber&#39;s CPE is equipped with the appropriate receiving and decoding circuitry, the subscriber can view the calling party&#39;s telephone number on a display device and decide whether or not to answer the telephone call.  
           [0006]    Some CPEs permit a subscriber to combine the CW and CID features in a single CPE (for example, CIDCW CPE) whereby the subscriber&#39;s CIDCW CPE displays a third party&#39;s CID information, (for example, the third party&#39;s name, telephone number, and any other information transmitted from the central office) while the subscriber is in communication with a second party. This allows the subscriber to make an informed decision as to whether or not to interrupt a current telephone call with the second party in order to answer the incoming call from the third party.  
           [0007]    Some subscribers find it convenient to have access to multiple telephone lines. Although there are various CPEs capable of handling multiple telephone lines, should a subscriber want to implement the CIDCW feature on each of the telephone lines, a separate CIDCW CPE for each of the telephone lines is generally required. Obviously, this can be cumbersome and expensive for the user.  
           [0008]    One solution may be to combine the circuitry from multiple CIDCW CPEs under a single housing. If so, the number of circuit elements needed to process CIDCW information for a single telephone line would be multiplied by the number of telephone lines the CPE is capable of handling. That is, for example, a two line CIDCW CPE would have two CID detectors (i.e., a separate CID detector for each telephone line). Of course, as the number of circuit elements within a CPE are multiplied, the size and cost of the CPE increases. Clearly, there is a need for a cost-effective CPE and method that is capable of detecting, receiving and processing CID information over a plurality of telephone lines.  
           [0009]    The CID and CIDCW features are well-known and are described in TR-NWT-000031, CLASS Feature: Calling Number Delivery, FSD 01-02-1090, (A module of LSSGR, FR NWT 000064) Issue 4 (Bellcore, December 1992) TR-NWT-000575, CLASS Feature: Calling Identify Delivery on Call Waiting, FSD 01-02-1090, (A module of LSSGR, FR-NWT-000064) Issue 1 (Bellcore, October 1992), plus Revision 1, December 1994, the entire disclosure of each is incorporated herein by reference.  
         OBJECTS AND SUMMARY  
         [0010]    It is therefore an object of the present invention to provide a multiple line customer premises equipment (CPE) that is capable of receiving caller identification (CID) information over a plurality of telephone lines.  
           [0011]    It is another object of the present invention to provide a multiple line CPE that is capable of handling the caller identification and call-waiting (CIDCW) feature over a plurality of telephone lines.  
           [0012]    It is a further object of the present invention to provide a cost-effective multiple line CPE capable of handling caller identification (CID) information with or without the call-waiting feature (CW) over a plurality of telephone lines.  
           [0013]    It is yet another object of the present invention to provide a multiple line CPE that utilizes a single circuit for detecting CID information over a plurality of telephone lines.  
           [0014]    It is yet a further object of the present invention to provide a multiple line CPE that is capable of selectively enabling and disabling the CID feature over any of the plurality of telephone lines.  
           [0015]    It is still another object of the present invention to provide a multiple line CPE that is capable of selectively enabling and disabling the CW feature over any of the plurality of telephone lines.  
           [0016]    It is still a further object of the present invention to provide a multiple line CPE that determines, based on a set of priorities, which one of a plurality of telephone lines on which to receive CID information.  
           [0017]    It is yet still another object of the present invention to display received CID information and on which of the plurality of telephone lines the CID information is received.  
           [0018]    In accordance with one form of the present invention, a customer premises equipment (CPE) is provided that is capable of accepting a plurality of telephone lines and receiving caller identification (CID) information from a central office on each of the plurality of telephone lines.  
           [0019]    According to an embodiment of the present invention, the CPE is able to process CID information over a plurality of telephone lines by dynamically switching the connection of a CID detector from one telephone line to another, depending on the current state of the CPE. For example, in a two-line, CIDCW embodiment of the present invention, if the CPE is first engaged on Line-1 and a ring is received on Line-2, the CID detector is switched to Line-2 in order to detect the CID information. After the CID information from Line-2 is received, if Line-1 is still off-hook, the CID detector is reconnected to Line-1 in order to be able to detect CIDCW information from a second call on Line-1. It should be noted that during this process, the telephone conversation on Line-1 is allowed to proceed uninterrupted. However, if Line-1 is no longer off-hook and Line-2 is now off-hook, the CID detector remains coupled to Line-2. When Line-2 goes back on-hook, the CID detector reconnects to Line-1.  
           [0020]    Switching a single CID detector between multiple telephone lines prevents the user from simultaneously receiving CID information over multiple telephone lines. However, the probability of receiving simultaneous telephone calls, particularly for a two-line CPE, has been determined to be relatively low. Therefore, the cost-savings in using the fewer components justifies the loss of that feature. Furthermore, since typical display components (i.e. liquid crystal displays) incorporated in most CID CPEs will display only one set of CID information at a time, simultaneously received CID information could not be simultaneously displayed.  
           [0021]    Still further, a user may choose not to subscribe to the CID or CIDCW feature for all of the available telephone lines or may choose not to utilize all of the available telephone line connections. Therefore, it would not be necessary for the CPE to switch the CID circuitry to those telephone lines which do not subscribe to the CID and/or CIDCW feature or to the telephone lines that are not connected to the CPE. In an embodiment of the present invention where a telephone line is connected to the CPE but does not subscribe to the CID or CIDCW feature, the user may selectively disable the CID or CIDCW feature for the specified telephone lines, to prevent the CID/CIDCW circuit from unnecessarily connecting to a particular telephone line. Hereinafter, the CID or CIDCW feature is considered “enabled” if the user subscribes to the respective feature and the CPE is not prevented from accepting any aspect of the respective feature.  
           [0022]    A user may incorporate the present invention in any number of devices available, including a corded telephone, a base unit speakerphone, a cordless handset, a computer having a modem, a video phone, or a facsimile machine.  
           [0023]    A preferred form of the apparatus and method which provides a cost effective CID and CW for a multiline telephone, as well as other embodiments, objects, features and advantages of this invention, will be apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    [0024]FIG. 1 is a block diagram of a two-line customer premises equipment (CPE) for providing caller identification (CID) information over two telephone lines in accordance with the present invention;  
         [0025]    [0025]FIG. 2 is a block diagram of a portion of an N-line CPE for providing CID information over N-telephone lines in accordance with the present invention;  
         [0026]    [0026]FIG. 3 is a flow diagram showing an embodiment of the operation of a two-line CID CPE for switching the two-line CID CPE&#39;s CID circuitry between two telephone lines having the CID feature enabled on both telephone lines, in accordance with the present invention;  
         [0027]    [0027]FIG. 4 is a flow diagram showing an embodiment of the operation of a two-line CID CPE for switching the two-line CID CPE&#39;s CID circuitry between two telephone lines, depending on whether the CID feature is enabled or disabled on the telephone lines, in accordance with the present invention;  
         [0028]    [0028]FIG. 5 is a partial flow diagram showing an embodiment of the operation of a two-line CIDCW CPE for switching the two-line CIDCW CPE&#39;s CID circuitry between two telephone lines, depending on whether the CW feature is enabled or disabled on the telephone lines, in accordance with the present invention;  
         [0029]    [0029]FIG. 6 is a flow diagram showing a continuation of the partial flow diagram of FIG. 5 if the CIDCW feature is enabled on both telephone lines in accordance with the present invention;  
         [0030]    [0030]FIG. 7 is a flow diagram showing a continuation of the partial flow diagram of FIG. 5 if the CIDCW feature is enabled on both telephone lines for a two-line CPE having a hold feature for each of the telephone lines, in accordance with the present invention;  
         [0031]    [0031]FIG. 8 a  is a partial flow diagram showing an embodiment of the operation of an N-line CIDCW CPE for switching the N-line CIDCW CPE&#39;s CID circuitry between N-telephone lines, each telephone line having the CIDCW feature enabled, in accordance with the present invention;  
         [0032]    [0032]FIG. 8 b  is a flow diagram showing a continuation of the partial flow diagram of FIG. 8 a;  and  
         [0033]    [0033]FIG. 9 is a flow diagram showing an embodiment of the operation for processing and displaying CID information, including the telephone line on which the CID information was received, in accordance with the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]    Referring to FIG. 1, a block diagram of a customer premises equipment (CPE)  10  for providing caller identification (CID) information over two telephone lines in accordance with a first embodiment of the present invention is shown. The CPE  10  includes a Line-1 circuit  20  coupled to the tip T 1  and ring R 1  leads of a first telephone line (Line-1)  32 . The Line-1 circuit  20  includes a first off-hook sensor  22  operably coupled to both the tip and ring leads of the first telephone line  32  for determining whether the first telephone line  32  is in an “on-hook” or “off-hook” condition. This information is provided to a microprocessor  38 . The line-1 circuit also includes a first ring detector  24  operably coupled to both the tip and ring leads of the first telephone line  32 . The ring detector  24  alerts the CPE  10  when an incoming call has arrived on the first telephone line  32  by providing ring detect signals to the microprocessor  38 . The Line-1 circuit also includes a first AC line interface  26  operably coupled to both the tip and ring leads of the first telephone line  32  for passing AC signals, such as CPE alerting signal (CAS) tones and modulated CID information, to a first leg  34   a  of a first single pole double throw (SPDT) switch  34 . The Line-1 circuit also includes a first transformer  28  operably coupled to the tip and ring leads of the first telephone line  32 , and a first hook switch  30  coupled to the transformer for selectively passing signals provided by the transformer to a first leg  42   a  of a second SPDT switch  42 .  
         [0035]    The CPE  10  also includes a Line-2 circuit  40  coupled to the tip T 2  and ring R 2  leads of a second telephone line (Line  2 )  54 . The Line-2 circuit  40  is similar to the Line-1 circuit  20  in form and function. The Line-2 circuit  40  includes a second off-hook sensor  44 , a second ring detector  46 , a second AC line interface  48 , a second transformer  50 , and a second hook switch  52 . The second AC line interface  48  passes AC signals from the second telephone line  62  to a second leg  34   b  of the first SPDT switch  34 . The second hook switch  52 , which is coupled to the transformer  50 , selectively passes signals provided by the transformer to a second leg  42   b  of the second SPDT switch  42 .  
         [0036]    In one embodiment of the present invention, each of the first and second AC line interfaces,  26  and  48 , comprises a differential amplifier circuit.  
         [0037]    The CPE  10  further includes a caller identification and call-waiting (CIDCW) detection circuit  36  operatively coupled to the first SPDT switch  34 . The CIDCW detection circuit  36  detects the CAS tones and CID information provided by the first and second AC line interfaces  26  and  48 . Although in the preferred embodiment of the present invention the CIDCW detection circuit  36  is incorporated in a single integrated circuit (IC), the CIDCW detection circuit  36  may be comprised of a separate CAS detector and CID detector (that is, discrete components). In the case of Type I Caller ID (CID without the CW feature), the CIDCW detection circuit  36  may be replaced with a CID detection circuit.  
         [0038]    Under the control of the microprocessor  38 , the first SPDT switch  34  switches between the output of the first AC line interface  26  (i.e. first leg  34   a ) and the output of the second AC interface  48  (i.e. second leg  34   b ). The microprocessor  38  is operatively coupled to the CIDCW detection circuit  36 , and depending on the position of the first SPDT switch  34 , will process caller identification (CID) information received from either Line-1 (i.e. first telephone line  32 ) or Line-2 (i.e. second telephone line  62 ). The microprocessor  38  is also operatively coupled to a display  60  for displaying the received and processed CID information. Alternatively, concurrently or subsequently, the CID information may be provided by the microprocessor  38  to a different device (not shown) for further processing of the CID information (e.g., a memory for storage, CID voice announcement device, etc.).  
         [0039]    The CPE  10  further includes a speech network  54  operatively coupled to the microprocessor  38  and the second SPDT switch  42 . Under the control of the microprocessor  38 , the second SPDT switch is alternately coupled between the output of the first hook switch  30  (i.e. first leg  42   a ) and the output of the second hook switch  52  (i.e. second leg  42   b ). A receiver  56  (e.g. an earphone or loudspeaker) is operatively coupled to the microprocessor  38  and the speech network  54  so that speech signals received from the telephone line circuits  20  and  40 , via the second SPDT switch  42 , may be processed and output by the receiver  56 . A microphone  58  is operatively coupled to the speech network  54  so that microphone (transmit) speech signals may be processed and passed to the appropriate telephone line circuit  20  or  40 , via the second SPDT switch  42 .  
         [0040]    After receiving notification of incoming CIDCW information via a CAS tone, the microprocessor  38  generates and transmits an acknowledgment signal (ACK) to the speech network  54  for transmission to the appropriate telephone line circuit  20  or  40 . In addition, if CPE  10  is engaged on telephone line  32  or  62  when a second call is received on the same telephone line, the microprocessor  38  generates and transmits a tone (BEEP) to the receiver  56  in order to notify the user of the second incoming call on the engaged telephone line.  
         [0041]    Referring now to FIG. 2, a block diagram of a CPE  11  in accordance with a second embodiment of the present invention is shown. FIG. 2 is similar to FIG. 1 except that the two-line embodiment is expanded to accommodate a plurality of telephone lines (i.e. N telephone lines), by employing switching devices capable of coupling to N telephone lines and increasing the number of circuit elements, as required, to accommodate the N telephone lines.  
         [0042]    The CPE  11  in accordance with the second embodiment includes a plurality of telephone line circuits coupled to a plurality of telephone lines (not shown) in a manner similar to the Line-1 circuit  20  (or Line-2 circuit  40 ) of FIG. 1. For example, for a six-line telephone, the first telephone line will connect to Line-1 circuit  20 , the second telephone line will connect to Line-2 circuit  40 , and so on. The fifth telephone line will connect to Line-(N-1) circuit  70  and the sixth telephone line will connect to Line-N circuit  80 .  
         [0043]    Similar in form and function to the telephone line circuits  20  and  40  in FIG. 1, the line circuits of FIG. 2 ( 20 ,  40 ,  70  and  80 ) each include an off-hook sensor, a ring detector, an AC line interface, a transformer, and a hook switch.  
         [0044]    In the second embodiment shown in FIG. 2, the first SPDT switch  34  (FIG. 1) is replaced with a first single pole, N-throw (SPNT) switch  90 , where N is equal to the number of telephone lines connected to CPE  11 . The second SPDT switch  42  of FIG. 1, is replaced with a second SPNT switch  92 . The balance of the CPE  11  circuitry is similar in form and function to that of CPE  10  of FIG. 1. Specifically, the CPE  11  includes CIDCW detection circuit  36 , microprocessor  38 , speech network  54 , receiver  56 , microphone  58 , and display  60 . As was mentioned in connection with the first embodiment, the CIDCW detection circuit  36  of the second embodiment may comprise a separate CAS detector and CID detector, and in the case of Type I Caller ID, the CIDCW detection circuit  36  may be replaced with a CID detection circuit.  
         [0045]    Referring now to FIG. 3, a flow diagram illustrating the operation of a two-line CID CPE for switching the two-line CID CPE&#39;s CID circuitry between two telephone lines having the CID feature enabled on both telephone lines in accordance with the present invention is shown. Initially, the CPE (ring detector  2 ,  46 ) determines if there is a ring signal on telephone Line-2 (Step  200 ). If there is a ring signal on Line-2 (YES in Step  200 ), a CID switch couples the CID circuit to Line-2 (Step  202 ) and the CPE checks for any CID information (Step D). At Step  200 , if there is no incoming call on Line-2 (NO in Step  200 ), the CID switch couples the CID circuit to telephone Line-1 (Step  204 ) and the CPE checks for any CID information (Step D). Therefore, the CPE sets the CID switch to couple the CID circuit to Line-1 unless there is a ring signal on Line-2.  
         [0046]    Referring now to FIG. 4, a flow diagram illustrating the operation of a two-line CID CPE for switching the two-line CID CPE&#39;s CID circuitry between two telephone lines, depending on whether the CID feature is enabled or disabled on the telephone lines, in accordance with the present invention is shown. Initially, the CPE determines if the CID feature is enabled for Line-2 (Step  220 ). If the CID feature is disabled for Line-2 (NO in Step  220 ), Line-2 will not receive CID data. Therefore, the CID switch always couples the CID circuit to Line-1 (Step  222 ) and the CPE checks for any CID information (Step D). At Step  220 , if the CID feature is enabled for Line-2 (YES in Step  220 ), the CPE determines if the CID feature is also enabled for Line-1 (Step  224 ). If the CID feature is disabled for Line-1 (NO in Step  224 ), Line-1 never receives CID data. Therefore, the CID switch always couples the CID circuit to Line-2 (Step  226 ) and the CPE checks for any CID information (Step D). At Step  224 , if the CID feature on Line-1 is enabled (YES in Step  224 ) which indicates that the CID feature of both Line-1 and Line-2 are enabled, the CPE determines if there is a ring signal on telephone Line-2 (Step  228 ). If there is a ring signal on Line-2 (YES in Step  228 ), a CID switch couples the CID circuit to Line-2 (Step  230 ) and the CPE checks for any CID information (Step D). At Step  228 , if there is no incoming call on Line-2 (NO in Step  228 ), the CID switch couples the CID circuit to telephone Line-1 (Step  232 ) and the CPE checks for any CID information (Step D).  
         [0047]    Referring now to FIG. 5, a partial flow diagram illustrating the operation of a two-line CIDCW CPE for switching the two-line CIDCW CPE&#39;s CID circuitry between two telephone lines, depending on whether the CW feature is enabled or disabled, in accordance with the present invention is shown. Initially, the CPE determines if the CW feature is enabled for Line-1 (Step  250 ). If the CW feature is disabled for Line-1 (NO in Step  250 ), the CPE determines if Line-1 is in an off-hook condition (Step  252 ). If Line-1 is off-hook (YES in Step  252 ), since the CW feature is disabled for Line-1 and will not be able to receive CID data over the occupied telephone line, a CID switch couples the CIDCW circuit to Line-2 (Step  254 ) and the CPE checks for any CID information (Step D). At Step  252 , if Line-1 is on-hook (NO in Step  252 ), the CPE determines if there is a ring signal on Line-1 (Step  256 ). If there is a ring signal on Line-1 (YES in Step  256 ), the CID switch couples the CIDCW circuit to Line-1 (Step  258 ) and the CPE checks for any CID information (Step D). At Step  256 , if there is no incoming call on Line-1 (NO in Step  256 ), the CID switch couples the CIDCW circuit to Line-2 (Step  260 ) and the CPE checks for a CAS tone or any CID information (Step D).  
         [0048]    Referring again to Step  250 , if the CW feature is enabled for Line-1 (YES in Step  250 ), the CPE determines if the CW feature is also enabled for Line-2 (Step  262 ). If the CW feature is enabled for Line-2 (YES in Step  262 ), the method must arbitrate further to determine which telephone line to couple the CID circuit (Step C) At Step  262 , if the CW feature is disabled for Line-2 (NO in Step  262 ), the CPE determines if Line-2 is in an off-hook condition (Step  264 ). If Line-2 is off-hook (YES in Step  264 ), since the CW feature is disabled for Line-2 and will not be able to receive CID data over the occupied telephone line, a CID switch couples the CIDCW circuit to Line-1 (Step  266 ) and the CPE checks for a CAS tone or any CID information (Step D). At Step  264 , if Line-2 is on-hook (NO in Step  264 ), the CPE determines if there is a ring signal on Line-2 (Step  268 ). If there is a ring signal on Line-2 (YES in Step  268 ), the CID switch couples the CIDCW circuit to Line-2 (Step  270 ) and the CPE checks for any CID data (Step D). At Step  268 , if there is no incoming call on Line-2 (NO in Step  268 ), the CID switch couples the CIDCW circuit to Line-1 (Step  272 ) and the CPE checks for a CAS tone or any CID information (Step D).  
         [0049]    Referring now to FIG. 6, a flow diagram which continues the flow diagram of FIG. 5 for the case where the CIDCW feature is enabled on both telephone lines in accordance with the present invention is shown. The CPE determines if there is a ring signal on telephone Line-1 (Step  300 ). If there is a ring signal on Line-1 (YES in Step  300 ), the CIDCW circuit is coupled to Line-1 (Step  302 ) and the CPE checks for any CID information (Step D). At Step  300 , if there is no incoming call on Line-1 (NO in Step  300 ), the CPE determines if there is a ring signal on telephone Line-2 (Step  304 ). If there is a ring signal on Line-2 (YES in Step  304 ), the CIDCW circuit is coupled to Line-2 (Step  306 ) and the CPE checks for any CID information (Step D). At Step  304 , if there is no incoming call on Line-2 (NO in Step  304 ), the CPE determines if the CPE is off-hook on Line-1 (Step  308 ). If the CPE is off-hook on Line-1 (YES in Step  308 ), then the CIDCW circuit is coupled to Line-1 (Step  310 ) in order to detect a second incoming call (via a CAS tone) on Line-1 (Step D). At Step  308 , if the CPE is on-hook on Line-1 (NO in Step  308 ), the CPE determines if it is off-hook on Line-2 (Step  312 ). If the CPE is off-hook on Line-2 (YES in Step  312 ), then the CIDCW circuit is coupled to Line-2 (Step  314 ) in order to detect a second incoming call (via a CAS tone) on Line-2 (Step D). At Step  312 , if the CPE is on-hook on Line-2 (NO in Step  312 ), the CPE determines if Line-1 is in use (i.e. another CPE is off-hook on Line-1) (Step  316 ). If Line-1 is in use (YES in Step  316 ), the CIDCW circuit is coupled to Line-1 (Step  318 ) and the CPE checks for any CID information (Step D). If Line-1 is not in use (NO in Step  316 ), the CPE determines if Line-2 is in use (Step  320 ). At Step  320 , if Line-2 is in use (YES in Step  320 ), the CIDCW circuit is coupled to Line-2 (Step  322 ) and the CPE checks for any CID information (Step D). If Line-2 is not in use (NO in Step  320 ), the CIDCW circuit is coupled to Line-1 (Step  324 ).  
         [0050]    Referring now to FIG. 7, a flow diagram which continues the flow diagram of FIG. 5 for the case where the CIDCW feature is enabled on both telephone lines and the CPE has a hold feature for each of the telephone lines in accordance with the present invention is shown. Initially, the CPE determines if there is a ring signal on telephone Line-1 (Step  350 ). If there is a ring signal on Line-1 (YES in Step  352 ), the CIDCW circuit is coupled to Line-1 (Step  352 ) and the CPE checks for any CID information (Step D). At Step  350 , if there is no incoming call on Line-1 (NO in Step  350 ), the CPE determines if there is a ring signal on telephone Line-2 (Step  354 ). If there is a ring signal on Line-2 (YES in Step  354 ), the CIDCW circuit is coupled to Line-2 (Step  356 ) and the CPE checks for any CID information (Step D). At Step  354 , if there is no incoming call on Line-2 (NO in Step  354 ), the CPE determines if the CPE is “active” on Line-1 (Step  358 ). That is, the CPE determines if the CPE is off-hook but not on hold. If the CPE is active on Line-1 (YES in Step  358 ), then the CIDCW circuit is coupled to Line-1 (Step  360 ) in order to be able to receive CID information from a second call on Line-1 (Step D). At Step  358 , if the CPE is not active on Line-1 (NO in Step  358 ), the CPE determines if it is active on Line-2 (Step  362 ). If the CPE is active on Line-2 (YES in Step  362 ), then the CIDCW circuit is coupled to Line-2 (Step  364 ) in order to be able to receive CID information from a second call on Line-2 (Step D). At Step  362 , if the CPE is not active on Line-2 (NO in Step  362 ), the CPE determines if Line-1 is in use (i.e. off-hook) (Step  366 ). If Line-1 is in use (YES in Step  366 ), the CPE determines if Line-1 of the CPE is on hold (Step  368 ). If Line-1 of the CPE is not on hold (NO in Step  368 ), the CIDCW circuit is coupled to Line-1 (Step  370 ) and the CPE checks for a CAS tone or any CID information (Step D). At Step  368 , if Line-1 of the CPE is on hold (YES in Step  368 ), the CPE determines if Line-2 of the CPE is on hold (Step  372 ). If Line-2 of the CPE is on hold (YES in Step  372 ), the CIDCW circuit is coupled to Line-1 (Step  374 ) and the CPE checks for a CAS tone or any CID information (Step D). At Step  372 , if the CPE is not on hold on Line-2 (NO in Step  372 ), the CPE determines if Line-2 is in use (Step  376 ).  
         [0051]    Once the CPE determines that a) Line-1 is not in use; or b) Line-1 of the CPE is on hold but Line-2 of the CPE is not on hold (either NO in Step  366  or NO in Step  372 ), the CPE determines if Line-2 is in use (Step  376 ). If Line-2 is in use (YES in Step  376 ), the CIDCW circuit is coupled to Line-2 (Step  378 ) and the CPE checks for a CAS tone or any CID information (Step D). At Step  376 , if Line-2 is not in use (NO in Step  376 ), the CIDCW circuit is coupled to Line-1 (Step  380 ) and the CPE checks for any CID information (Step D).  
         [0052]    The CPE prioritizes the events that determine when the CID circuit will be coupled to any given telephone line. In the preferred embodiment of the invention, the order of priority is: 1) whether a ring signal is received on a telephone line; 2) whether the CPE is off-hook on a telephone line; 3) whether there is a telephone line in use on a telephone line in which the CPE is not on hold; and 4) whether the CPE is on hold on a telephone line. In the preferred embodiment, if both telephone lines are of the same priority, higher consideration is given to Line-1 over Line-2. Of course, Line-2 could just as well be given higher priority without affecting the scope of the present invention.  
         [0053]    Referring now to FIGS. 8 a  and  8   b,  a flow diagram illustrating the operation of an N-line CPE for switching the N-line CPE&#39;s CIDCW circuitry between N telephone lines, depending on whether the CIDCW feature is enabled or disabled, in accordance with the present invention is shown. FIGS. 8 a  and  8   b  are similar to FIG. 7 except that the two-line embodiment is expanded to accommodate a plurality of telephone lines (i.e. N telephone lines). The order of priorities in determining when the CIDCW circuit will be coupled to any given telephone line is the same as for the two-line CPE. Specifically, the order of priorities: is 1) whether a ring signal is received on a telephone line (Steps  400 - 422 ); 2) whether the CPE is active on a telephone line (Steps  424 - 446 ); 3) whether there is a telephone line in use in which the CPE is not on hold (Steps  448 - 478 ); and 4) whether the CPE is on hold on a telephone line (Steps  480 - 502 ). If none of the preceding priorities apply, the CIDCW circuit will be coupled to Line-1 (Step  504 ) and the CPE checks for any CID information (Step D).  
         [0054]    In the preferred embodiment, when there are multiple lines of the same priority, the lower numbered telephone line is given first consideration. For example, if Line-2 and Line- 4  both receive ring signals at the same time, the CIDCW circuit will be coupled to Line-2 (the lower numbered telephone line).  
         [0055]    It will be appreciated that a set of priorities may be established for a CPE that has CID without the CW feature. In such a case, the priorities are preferably: 1) whether a ring signal is received on a telephone line; and 2) whether the CPE is on-hook on a telephone line, ordered respectively.  
         [0056]    Referring now to FIG. 9, a flow diagram illustrating the operation for processing and displaying CID information, including the telephone line on which the CID information was received, in accordance with the present invention is shown. Once the CID circuit is operatively connected to a telephone line, the CPE checks for a CAS tone, CID information, or other modulated signals sent from the central office (Step  600 ). If such modulated signals are not detected (NO in Step  600 ), the operation is abandoned and the method ends. At Step  600 , if modulated signals are detected (YES in Step  600 ), the signals (i.e. CID data) are received and processed (Step  602 ) for display by the CPE (Step  604 ). At Step  604 , the CPE also displays the appropriate telephone line in which the CID data was received (line status). The CID data and telephone line status are then stored for further processing (Step  606 ) and the method ends. The method of receiving, processing and displaying the CID data is well known in the art and therefore need not be explained in detail herein.  
         [0057]    Having described the principles and preferred embodiments of the invention with reference to the accompanying drawings, it will be appreciated that the present invention is not limited to those specific embodiments, and that various modifications can be effected thereto by one of ordinary skill in the art without departing from the scope or spirit of the invention, as defined in the appended claims.