Abstract:
A method of using an intercom on a cordless telephone during an active call. The active call is put on hold while the intercom is in use. Once the call is re-activated, the intercom is shut off. This system may be designed for a cordless telephone with one handset or a plurality of handsets.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The instant application is a divisional of co-pending U.S. application Ser. No. 13/367,957, filed Feb. 7, 2012, which is a continuation of U.S. application Ser. No. 09/777,889, filed Feb. 7, 2001, the disclosures of both of which are hereby incorporated by reference into the instant application. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a method and apparatus for operating a cordless telephone during an active call. 
       BACKGROUND OF THE INVENTION 
       [0003]    Some cordless telephones have intercoms which allow a person near a base station to speak to a person who has a handset. These telephones, however, do not allow the intercom function to be used during an active call. 
         [0004]    What is needed is a convenient way for the person who answers a call with the cordless handset to communicate to the intended recipient via the intercom function that the call is for him/her. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention overcomes the problems associated with the prior art and provides a unique method and system for allowing a user of a cordless phone telephone handset to use the intercom while a call is active. 
         [0006]    In accordance with one aspect of the present invention, the system has a base station and one cordless handset. An intercom communication initiated at either location will cause an active call at either location to be automatically placed on hold for the duration of the intercom communication after which the active call is re-engaged 
         [0007]    In another aspect of the invention, an active call can be automatically placed on hold during an intercom communication in cordless telephone systems which have more than one handset. 
         [0008]    The above and other advantages and features of the invention will be more readily understood from the following detailed description of the invention which is provided in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a block diagram of an active call intercom enabled cordless telephone with one handset; 
           [0010]      FIG. 2   a  is a flowchart of the algorithm to initiate an intercom communication in the base station of an active call intercom enabled single handset cordless telephone; 
           [0011]      FIG. 2   b  is a flowchart of the algorithm to end an intercom communication in the base station of an active call intercom enabled single handset cordless telephone; 
           [0012]      FIG. 2   c  is a flowchart of the algorithm in the handset of an active call intercom enabled single handset cordless telephone; 
           [0013]      FIG. 3  is a block diagram of an active call intercom enabled multiple handset cordless telephone; 
           [0014]      FIG. 4   a  is a flowchart of the algorithm in the base station of an active call intercom enabled multiple handset cordless telephone. 
           [0015]      FIG. 4   b  is a flowchart of the algorithm in a handset of an active call intercom enabled multiple handset cordless telephone. 
           [0016]      FIG. 5  is a block diagram of a multiple handset active call intercom enabled cordless telephone with separate intercoms for each handset; 
           [0017]      FIG. 6   a  is a flowchart of the algorithm in the Base station of a multiple handset active call intercom enabled cordless telephone with separate intercoms for each handset; 
           [0018]      FIG. 6   b  is a continuation of the flowchart of the algorithm in the Base station of a multiple handset active call intercom enabled cordless telephone with separate intercoms for each handset; 
           [0019]      FIG. 6   c  is a continuation of the flowchart of the algorithm in the Base station of a multiple handset active call intercom enabled cordless telephone with separate intercoms for each handset; 
           [0020]      FIG. 6   d  is a flowchart of the algorithm in a handset of a multiple handset active call intercom enabled cordless telephone with separate intercoms for each handset; 
           [0021]      FIG. 6   e  is a continuation of the flowchart of the algorithm in the base station of a multiple handset active call intercom enabled cordless telephone with separate intercoms for each handset. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that structural changes may be made and equivalent structures substituted for those shown without departing from the spirit and scope of the present invention. 
         [0023]    In a first embodiment of the invention, illustrated in  FIGS. 1 ,  2   a,    2   b,    2   c,  a cordless telephone system is shown ( FIG. 1 ) which includes a base station  1000  and a handset  1010 . The base station  1000  includes a transmitter/receiver circuit  1001 , a line interface  1002 , an intercom button  1003 , a microprocessor  1004 , a speaker/microphone  1005 , and a speakerphone button  1006 . Handset  1010  includes a transmitter/receiver circuit  1011 , a speaker/microphone  1012 , a microprocessor  1013 , an intercom button  1014 , and an activate line button  1015 . The base station  1000  may have a speakerphone which is a speaker/microphone  1005  combination or a hardwired handset which also includes a speaker/microphone combination  1005 . 
         [0024]    In accordance with the first embodiment of a cordless telephone system of the present invention, the cordless handset  1010  has an intercom button  1014 , which if depressed while handset  1010  has an active call, automatically puts the call on hold and initiates an intercom communication between handset  1010  and base station  1000 . A call is active when a person is speaking to someone on the telephone at either base station  1000  or handset  1010 . If the intercom button  1003  at the base station  1000  is depressed while the base station  1000  has an active call, the active call is automatically put on hold and an intercom communication from the base station  1000  to handset  1010  is initiated. If the intercom button  1003  at the base station  1000  is depressed while handset  1010  has an active call, handset  1010  alerts the handset user that the base station  1000  wants to initiate an intercom communication. If the handset  1010  user then presses the intercom button  1014 , the active call is automatically put on hold and the intercom is initiated. If an intercom button  1014  at handset  1010  is depressed while the base station  1000  has an active call, the base station  1000  alerts the base station  1000  user that the handset  1010  user wants to initiate an intercom communication. If the base station  1000  user then presses the intercom button  1003 , the active call is automatically put on hold and the intercom is initiated. 
         [0025]    Referring first to the base station processing illustrated in  FIG. 2   a,    FIGS. 2   a,    2   b  illustrate processing respectively performed at the base station  1000  and handset  1010  by respective microprocessors  1004  and  1013  to implement the invention. When the base station  1000  receives an intercom signal transmitted from handset  1010  at processing segment  1100 , indicating that the handset  1010  user wants to initiate an intercom communication, the microprocessor  1004  checks if the telephone line is active on handset  1010  at processing segment  1102 . If the telephone line is active on handset  1010 , then the transmitter/receiver circuit  1001  is disconnected from the telephone line at segment  1105 , the active line is placed on hold, and the transmitter/receiver circuit  1001  is connected to the speaker/microphone  1005  at segment  1106 , initiating the intercom communication. If the telephone line is not active on handset  1010 , the microprocessor  1004  checks if the telephone line is active at the base station  1000  at processing segment  1103 . If the telephone line is active at the base station  1000 , the telephone line is disconnected from the speaker microphone  1006  at segment  1107 , the active line is placed on hold, and the transmitter/receiver circuit  1001  is connected to the speaker/microphone  1006  at segment  1108 , initiating the intercom communication. If the telephone line is not active at the base station  1000 , then the transmitter/receiver circuit  1001  is connected to the speaker/microphone  1005  at segment  1104 . 
         [0026]    If the intercom button signal from handset  1010  is not received by the base station  1000 , as detected at processing segment  1100 , the microprocessor  1004  checks if the base station&#39;s intercom button  1003  was depressed at processing segment  1110 , indicating that the base station user wants to initiate an intercom communication. If the intercom button  1003  was not depressed, as detected processing segment  1110 , the microprocessor returns to the start of base station processing because nothing has happened. 
         [0027]    If the intercom button  1003  was depressed, as detected at processing segment  1110 , the microprocessor  1004  checks if the telephone line is active at the base station  1000  at processing segment  1111 . If the telephone line is active at the base station  1000 , as detected at processing segment  1111 , the telephone line is disconnected from the speaker/microphone  1006  at segment  1120 , putting the call on hold, the transmitter/receiver circuit  1001  is connected to the speaker/microphone  1005  at segment  1121 , initiating the intercom communication, and the intercom signal is transmitted from the base station  1000  to handset  1010  at segment  1122 . 
         [0028]    If the telephone line is not active at the base station  1000 , as detected at processing segment  1111 , then the microprocessor  1004  checks if the telephone line is active on handset  1010  at processing segment  1112 . If the telephone line is not active on handset  1010 , as detected at processing segment  1112 , transmitter/receiver circuit  1001  is connected to the speaker/microphone  1006  at segment  1113 , initiating the intercom communication, and the intercom signal is transmitted from the base station  1000  to handset  1010  at segment  1117 . If the telephone line is active on handset  1010 , as detected at processing segment  1112 , the telephone line is disconnected from the transmitter/receiver circuit  1001  at segment  1114 , putting the telephone line on hold, the transmitter/receiver circuit  1001  is connected to the speaker/microphone  1006  at segment  1115 , initiating the intercom communication, and the intercom signal is transmitted from the base station  1000  to handset  1010  at segment  1116 . 
         [0029]    As illustrated in  FIG. 2   b,  after the intercom communication is initiated at segments  1104 ,  1106 ,  1108 ,  1108 ,  1116 ,  1117 , and  1122 , the microprocessor  1004  proceeds to check if the intercom communication should be terminated. The microprocessor  1004  checks if the intercom signal from handset  1010  was received at the base station  1000  at processing segment  1130 , indicating that the handset user wants to terminate the intercom communication, i.e. pressed the intercom button. If the intercom button signal from handset  1010  was received at the base station  1000 , as detected at processing segment  1130 , the transmitter/receiver circuit  1001  is disconnected from the speaker/microphone  1006  at segment  1131 , terminating the intercom communication. 
         [0030]    If the intercom button signal from handset  1010  is not received by the base station  1000 , as detected at processing segment  1130 , the microprocessor  1004  checks if the base station&#39;s intercom button  1003  was depressed at processing segment  1138 , indicating that the base station user wants to terminate the intercom communication. If the base station&#39;s intercom button  1003  was depressed, as detected at processing segment  1138 , the microprocessor  1004  transmits the end intercom signal to handset  1010  at segment  1140 , disconnects the transmitter/receiver circuit  1001  from the speaker/microphone  1006  at segment  1131 , terminating the intercom communication, and returns to the start of base station processing. 
         [0031]    If the base station&#39;s intercom button  1003  was not depressed, as detected at processing segment  1138 , the microprocessor  1004  checks if the speakerphone button  1006  (i.e. the base station&#39;s activate line button) was depressed at processing segment  1132 , indicating that the base station user wants to terminate the intercom communication and activate the telephone line. If the speakerphone button  1006  was depressed, as detected at processing segment  1132 , the transmitter/receiver circuit  1001  is disconnected from the speaker/microphone  1005  at segment  1133 , terminating the intercom communication, the telephone line is connected to speaker/microphone  1005  at segment  1134 , activating the line at the base station, and the end intercom signal is transmitted by the base station  1000  to handset  1010  at segment  1139 . 
         [0032]    If the speakerphone button  1006  is not depressed, as detected at processing segment  1132 , the microprocessor  1004  checks if an activate line signal from handset  1010  is received at base station  1000  at processing segment  1135 , indicating that the handset  1010  user wants to terminate the intercom communication and activate the line, i.e. pressed activate line button  1015  on handset  1010 . If an activate line signal is received by the base station  1000  from handset  1010 , as detected at processing segment  1135 , the transmitter/receiver circuit  1001  is disconnected from the speaker/microphone  1005  at segment  1136 , terminating the intercom communication. Then, the telephone line is connected to transmitter/receiver circuit  1001  at segment  1137 , activating the telephone line on handset  1010 . 
         [0033]    If an activate line signal is not received by the base station  1000  from handset  1010 , as detected at processing segment  1135 , the microprocessor  1004  returns to processing segment  1130  and continues the loop until the intercom communication should be terminated. 
         [0034]      FIG. 2   c  illustrates the process flow at handset  1010 . If the intercom button  1014  is not depressed, as detected at processing segment  1200 , the microprocessor  1013  checks if the intercom signal from base station  1000  is received at handset  1010  at processing segment  1210 , indicating that the base station user wants to initiate an intercom communication. If the intercom signal from base station  1000  is not received at handset  1010 , as detected at processing segment  1210 , the microprocessor returns to the start of handset processing. 
         [0035]    When handset  1010  intercom button  1014  is depressed, as detected at processing segment  1200 , the intercom button  1014  signal is transmitted by handset  1010  to the base station  1000  at segment  1201 , indicating that an intercom communication should be initiated. Handset  1010  then checks if the telephone line is active at handset  1010  at processing segment  1202 . If the telephone line is not active on handset  1010 , as detected at processing segment  1202 , the speaker/microphone  1012  is connected to the transmitter/receiver circuit  1011  at segment  1203  preparing the cordless handset for an intercom communication. The microprocessor  1013  then proceeds to processing segment  1214  to determine if the intercom communication should be terminated. 
         [0036]    If the intercom signal from base station  1000  is received by handset  1010  at processing segment  1210 , requesting an intercom communication, handset  1010  sends a signal to the speaker/microphone  1012  to beep at segment  1211  to alert the user that an intercom communication is requested. The microprocessor  1013  then checks if the intercom button  1014  was depressed at processing segment  1212 , indicating that the handset user also wants to initiate an intercom communication. If the intercom button was not depressed, as detected at processing segment  1212 , the microprocessor  1013  checks if the end intercom signal from base station  1000  was received by handset  1010  at processing segment  1220 , indicating that the base station user no longer wants to initiate an intercom communication. If the end intercom signal from base station  1000  was received by handset  1010 , as detected at processing segment  1220 , indicating that the request for an intercom communication has been removed, handset  1010  returns to the start of handset processing. If the end intercom signal from base station  1000  was not received by handset  1010 , handset  1010  returns to segment  1211  to alert the user again that an intercom communication is requested. 
         [0037]    If the intercom button was depressed, as detected at processing segment  1212 , indicating that the handset user also wants to initiate an intercom communication, then the microprocessor  1013  checks if the telephone line is active on handset  1010  at processing segment  1213 . If the telephone line is not active, as detected at processing segment  1213 , the speaker/microphone  1012  is connected to the transmitter/receiver circuit  1011  at segment  1221 , preparing handset  1010  for an intercom communication. Once the intercom communication is initiated at segment  1221 , the microprocessor  1013  proceeds to processing segment  1214  to determine if the intercom communication should be terminated. If the line is active, as detected at processing segment  1213 , handset  1010  is already prepared for an intercom communication and the microprocessor proceeds to processing segment  1214  to determine if the intercom communication should be terminated. 
         [0038]    Once the intercom communication is initiated, the microprocessor  1013  checks if the activate line button  1015  was depressed at processing segment  1214 , indicating that the intercom communication should be terminated and the line activated. If the activate line button was depressed, as detected at processing segment  1214 , then handset  1010  sends an activate line signal to the base station  1000  at segment  1215 . The microprocessor  1013  then proceeds to the start of handset processing. 
         [0039]    If the activate line button was not depressed, as detected at processing segment  1214 , the microprocessor  1013  checks if the intercom button  1014  was depressed at processing segment  1222 , indicating that the intercom communication should be terminated. If the intercom button  1014  was depressed, as detected at processing segment  1222 , indicating that the intercom communication should be terminated, then handset  1010  sends the intercom button  1014  signal to the base station  1000  at segment  1223  and disconnects the speaker/microphone  1012  from the transmitter/receiver circuit  1011  at segment  1224 . 
         [0040]    If the intercom button  1014  was not depressed, as detected at processing segment  1222 , the microprocessor  1013  checks if the end intercom signal from base station  1000  was received by handset  1010  at processing segment  1216 , indicating that the base station  1000  user wants to terminate the intercom communication. If the end intercom signal from base station  1000  was received by handset  1010 , as detected at processing segment  1216 , handset  1010  disconnects the speaker/microphone  1012  from the transmitter/receiver circuit  1011  at segment  1217  and returns to processing segment  1200 . If the end intercom signal from base station  1000  is not received by handset  1010 , as detected at processing segment  1216 , the microprocessor  1013  returns to processing segment  1214  to continue checking for an indication that the intercom communication should be terminated. 
         [0041]    Accordingly, no matter which of the base station  1000  and handset  1010  initiates an intercom communication during an active call, the active call is placed on hold during the intercom communication and is resumed when the intercom communication is over. 
         [0042]      FIGS. 3 ,  4  and  4   b  show a second embodiment which includes, as shown in  FIG. 3 , a base station  2000  a first handset  2010  and a second handset  2020 . The base station includes a transmitter/receiver circuit  2001 , a line interface  2002 , an intercom button  2003 , a microprocessor  2004 , a speaker/microphone  2005 , and a speakerphone button  2006 . Handset  2010  includes a transmitter/receiver circuit  2011 , a speaker/microphone  2012 , a microprocessor  2013 , an intercom button  2014 , and an activate line button  2015 . Handset  2020  includes a transmitter/receiver circuit  2021 , a speaker/microphone  2022 , a microprocessor  2023 , an intercom button  2024 , and an activate line button  2025 . The base station  2000  may have a speakerphone which is a speaker/microphone  2005  combination or a hardwired handset which also includes a speaker/microphone  2005  combination. 
         [0043]    When the intercom button  2014  or  2024  is depressed on a handset  2010  or  2020  where the call is active, the call is automatically put on hold and the intercom is initiated between all handsets  2010  and  2020  and the base station  2000 . When the intercom button  2003  is depressed at the base station  2000  while the call is active at the base station  2000 , the call is automatically put on hold and handsets  2010  and  2020  alert any users that the base station  2000  wants to initiate an intercom. If either handset  2010  or  2020  then depresses its intercom button  2014  or  2024 , the intercom is initiated. Otherwise, if the base station  2000  activate line button  2006  is depressed, the telephone line is re-activated. If the base station  2000  intercom button  2003  is depressed, the call is left on hold and handsets  2010  and  2020  end the intercom notification. When one of the intercom buttons  2003 ,  2014  or  2015  is depressed while the telephone line is active in another location, the intercom is not initiated until the active location depresses the intercom button  2003 ,  2014  or  2015 . 
         [0044]      FIG. 4   a  illustrates process flow for the base station  2000  of the second embodiment of the invention. When the base station  2000  does not receive an intercom signal from a handset  2010  or  2020  at processing segment  2100 , it checks if the intercom button  2003  was depressed at processing segment  2130 . If the intercom button  2003  is not depressed, as detected at processing segment  2130 , the microprocessor  2004  returns to processing segment  2100 . 
         [0045]    If an intercom button  2003  signal is received from handset  2010  or  2020  at processing segment  2100 , indicating that handset user wants to initiate an intercom communication, the microprocessor  2004  checks if the telephone line is active at processing segment  2101 . If the telephone line is inactive, as detected at processing segment  2101 , the base station  2000  transmits an intercom signal to handsets  2010  and  2020  at segment  2102  and connects the transmitter/receiver circuit  2001  to the speaker/microphone  2005  at segment  2103  initiating the intercom communication. 
         [0046]    If the telephone line is active, as detected at processing segment  2101 , the microprocessor  2004  checks if the telephone line is active in the same location as the intercom signal originated at processing segment  2110 . If the telephone line is active in the same place, as detected at processing segment  2110 , the base station  2000  disconnects the transmitter/receiver circuit  2001  from the telephone line at segment  2120  and connects the transmitter/receiver circuit  2001  to the speaker/microphone  2005  at segment  2121  initiating the intercom communication. 
         [0047]    If the telephone line is active in a different place than the intercom signal originated, as detected at processing segment  2110 , then the base station  2000  transmits an intercom signal at segment  2111  indicating to the other locations that a user wants to initiate an intercom communication. If an intercom signal from a handset  2010  or  2020  is not received by base station  2000 , as detected at processing segment  2112 , the microprocessor  2004  checks if the intercom button  2003  is depressed at processing segment  2115 , indicating that the base station user no longer wants to initiate an intercom communication. If the intercom button  2003  is depressed, as detected at processing segment  2115 , the microprocessor  2004  returns to the start of base station processing. If the intercom button is not depressed, as detected at processing segment  2115 , then the microprocessor  2004  returns to processing segment  2112  to continue the loop until the intercom is initiated or cancelled. 
         [0048]    If an intercom signal from a handset  2010  or  2020  is received by base station  2000 , as detected at processing segment  2112 , indicating that the active handset user also wants to initiate an intercom communication, the telephone line is disconnected from the transmitter/receiver circuit  2001  at segment  2113  and the transmitter/receiver circuit  2001  is connected to the speaker/microphone  2005  at segment  2114  initiating an intercom communication. 
         [0049]    If the intercom button  2003  is depressed, as detected at processing segment  2130 , indicating that the base station  2000  user wants to initiate an intercom communication, then the microprocessor  2004  checks if the telephone line is active at the base station  2000  at processing segment  2131 . If the telephone line is active at the base station  2000 , as detected at processing segment  2130 , then the base station  2000  disconnects the telephone line from the speaker/microphone  2005  at segment  2140 , connects the transmitter/receiver circuit  2001  to the speaker/microphone  2005  at segment  2141 , and transmits an intercom signal at segment  2142 , initiating the intercom communication. 
         [0050]    If the telephone line is inactive at the base station  2000 , as detected at processing segment  2131 , the microprocessor  2004  checks if the telephone line is active on a handset  2010  or  2020  at processing segment  2132 . If the telephone line is not active on a handset  2010  or  2020 , as detected at processing segment  2132 , the base station  2000  connects the transmitter/receiver circuit  2001  to the speaker/microphone  2005  at segment  2133  and transmits an intercom signal to handsets  2010  and  2020  at segment  2134 , initiating the intercom communication. 
         [0051]    If the telephone line is active on a handset  2010  or  2020 , as detected at processing segment  2132 , the base station  2000  disconnects the telephone line from the transmitter/receiver circuit  2001  at segment  2135 , connects the transmitter/receiver circuit  2001  to the speaker/microphone  2005  at segment  2136 , and transmits an intercom signal at segment  2137 , initiating the intercom communication. 
         [0052]    After the intercom communication is initiated at segments  2103 ,  2114 ,  2121 ,  2142 ,  2135 , and  2134 , the base station  2000  determines if the intercom communication should be terminated. The microprocessor  2004  checks if the activate line button signal is received at processing segment  2150 , indicating that the handset  2010  or  2020  user wants to terminate the intercom communication and activate the line. If the activate line button signal is received, as detected at processing segment  2150 , the base station  2000  disconnects the transmitter/receiver circuit  2001  from the speaker/microphone  2005  at segment  2151 , terminating the intercom communication, connects the telephone line and transmitter/receiver circuit  2001  at segment  2152 , activating the line at handset  2010  or  2020 , transmits the end intercom signal at segment  2153  and returns to the start of base station processing. 
         [0053]    If the activate line button signal is not received, as detected at processing segment  2150 , the microprocessor  2004  checks if the speakerphone button  2006  was depressed at processing segment  2160 , indicating that the base station  2000  user wants to terminate the intercom communication and activate the line at the base station  2000 . If the speakerphone button  2006  is depressed, as detected at processing segment  2160 , the base station  2000  disconnects the transmitter/receiver circuit  2001  from the speaker/microphone  2005  at segment  2161 , terminating the intercom communication, connects the telephone line and speakerphone  2006  at segment  2162 , activating the line at the base station, transmits the end intercom signal at segment  2163 , and returns the start of base station processing. 
         [0054]    If the speakerphone button is not depressed, as detected at processing segment  2160 , the microprocessor  2004  checks if the intercom signal from a handset  2010  or  2020  is received at processing segment  2164 , indicating that the handset  2010  or  2020  user wants to terminate the intercom communication. If the intercom signal from a handset  2010  or  2020  is received by base station  2000 , as detected at processing segment  2164 , the base station  2000  disconnects the transmitter/receiver circuit  2001  from the speaker/microphone  2005  at segment  2165 , terminating the intercom communication, transmits the end intercom signal to handsets  2010  and  2020  at segment  2163 , and returns to the start of base station processing. 
         [0055]    If the intercom signal from a handset  2010  or  2020  is not received by base station  2000 , as detected at processing segment  2164 , the microprocessor  2004  checks if the intercom button  2003  was depressed at processing segment  2166 , indicating that the base station  2000  user wants to terminate the intercom communication. If the intercom button was depressed, as detected at  2166 , the base station  2000  disconnects the transmitter/receiver circuit  2001  at segment  2165 , terminating the intercom communication, transmits the end intercom signal at segment  2163 , and returns to processing segment  2100 . 
         [0056]    If the intercom button is not depressed, as detected at processing segment  2166 , the microprocessor  2004  returns to processing segment  2150  to repeat the loop until the intercom communication should be terminated. 
         [0057]      FIG. 4   b  illustrates the process flow at handset  1   2010 . The process flow for handset  2   2020  is identical. If the intercom button  2014  is not depressed, as detected at processing segment  2200 , the microprocessor  2013  checks if the intercom signal from base station  2000  is received by handset  2010  at processing segment  2210 , indicating that the base station user or the handset  2  user wants to initiate an intercom communication. If the intercom signal from base station  2000  is not received by handset  2010 , as detected at processing segment  2210 , the microprocessor returns to the start of handset  1  processing. 
         [0058]    When handset  1   2010  intercom button  2014  is depressed, as detected at processing segment  2200 , the intercom button  2014  signal is transmitted by handset  1   2010  to the base station  2000  at segment  2201 , indicating that an intercom communication should be initiated. Handset  1   2010  then checks if the telephone line is active at handset  1   2010  at processing segment  2202 . If the telephone line is not active at handset  1   2010 , as detected at processing segment  2202 , the speaker/microphone  2012  is connected to the transmitter/receiver circuit  2011  at segment  2203  preparing handset  1  for an intercom communication. The microprocessor  2013  then proceeds to processing segment  2214  to determine if the intercom communication should be terminated. 
         [0059]    If the intercom signal from base station  20000  is received from handset  1   2010  at processing segment  2210 , requesting an intercom communication, handset  1   2010  sends a signal to the speaker/microphone  2012  to beep at segment  2211  to alert the user that an intercom communication is requested. The microprocessor  2013  then checks if the intercom button  2014  was depressed at processing segment  2212 , indicating that the handset  1  user also wants to initiate an intercom communication. If the intercom button was not depressed, as detected at processing segment  2212 , the microprocessor  2013  checks if the end intercom signal from base station  2000  was received by handset  1   2010  at processing segment  2220 , indicating that the base station  2000  user or the handset  2   2020  user no longer wants to initiate an intercom communication. If the end intercom signal from base station  2000  was received by handset  1   2010 , as detected at processing segment  2220 , indicating that the request for an intercom communication has been cancelled, handset  1   2010  returns to the start of handset  1  processing. If the end intercom signal from base station  2000  was not received by handset  1   2010 , as detected at processing segment  2220 , handset  1   2010  returns to segment  2211  to alert the user again that an intercom communication is requested. 
         [0060]    If the intercom button was depressed, as detected at processing segment  2212 , indicating that the handset  1  user also wants to initiate an intercom communication, then the microprocessor  2013  checks if the telephone line is active on handset  1   2010  at processing segment  2213 . If the telephone line is not active, as detected at processing segment  2213 , the speaker/microphone  2012  is connected to the transmitter/receiver circuit  2011  at segment  2221 , preparing handset  1   2010  for an intercom communication. Once the intercom communication is initiated at segment  2221 , the microprocessor  2013  proceeds to processing segment  2214  to determine if the intercom communication should be terminated. If the line is active, as detected at processing segment  2213 , handset  2010  is already prepared for an intercom communication and the microprocessor proceeds to processing segment  2214  to determine if the intercom communication should be terminated. 
         [0061]    Once the intercom communication is initiated, the microprocessor  2013  checks if the activate line button  2015  was depressed at processing segment  2214 , indicating that the intercom communication should be terminated and the line activated at handset  1 . If the activate line button was depressed, as detected at processing segment  2214 , then handset  1   2010  sends an activate line signal to the base station  2000  at segment  2215 . The microprocessor  2013  then proceeds to the start of handset  1  processing. 
         [0062]    If the activate line button was not depressed, as detected at processing segment  2214 , the microprocessor  2013  checks if the intercom button  2014  was depressed at processing segment  2222 , indicating that the intercom communication should be terminated. If the intercom button  2014  was depressed, as detected at processing segment  2222 , indicating that the intercom communication should be terminated, then handset  1   2010  sends the intercom button  2014  signal to the base station  2000  at segment  2223  and disconnects the speaker/microphone  2012  from the transmitter/receiver circuit  2011  at segment  2224 . 
         [0063]    If the intercom button  2014  was not depressed, as detected at processing segment  2222 , the microprocessor  2013  checks if the end intercom signal from base station  2000  was received by handset  1   2010  at processing segment  2216 , indicating that the base station  2000  user or the handset  2  user wants to terminate the intercom communication. If the end intercom signal from base station  2000  was received by handset  1   2010 , as detected at processing segment  2216 , handset  1   2010  disconnects the speaker/microphone  2012  from the transmitter/receiver circuit  2011  at segment  2217  and returns to processing segment  2200 . If the end intercom signal from base station  2000  is not received by handset  1   2010 , as detected at processing segment  2216 , the microprocessor  2013  returns to processing segment  2214  to continue checking for an indication that the intercom communication should be terminated. 
         [0064]    Accordingly, no matter which of the base station  2000 , handset  1   2010 , or handset  2   2020  initiates an intercom communication during an active call, the active call is placed on hold during the intercom communication and is resumed when the intercom communication is over. 
         [0065]      FIGS. 5 ,  6 ,  6   a,    6   b,    6   c,    6   d  and  6   e  show a third embodiment of the invention which includes, as shown in  FIG. 5  a base station  3000  a first handset  3010  and a second handset  3020 . Unlike the cordless telephone system show in  FIG. 3 , the present embodiment has separate intercom buttons for each other unit. This allows it allows an intercom communication that does not include all of the handsets or the base station. In addition, this system allows intercom communications between inactive units while another unit is active. The base station  3000  includes a first transmitter/receiver circuit  3002 , a second transmitter/receiver circuit  3001 , a line interface  3003 , a first intercom button  3004 , a second intercom button  3006 , a microprocessor  3005 , a speaker/microphone  3007 , and a speakerphone button  3008 . The first handset  3010  includes a transmitter/receiver circuit  3011 , a speaker/microphone  3012 , a microprocessor  3013 , an activate line button  3014 , a first intercom button  3016 , and a second intercom button,  3015 . The second handset  3020  includes a transmitter/receiver circuit  3021 , a speaker/microphone  3022 , a microprocessor  3023 , an activate line button  3024 , a first intercom button  3026 , and a second intercom button,  3025 . The base station  3000  may have a speakerphone which is a speaker/microphone  3005  combination or a hardwired handset which also includes a speaker/microphone  3005  combination. 
         [0066]    In accordance with the third embodiment of the invention, when a handset  3010  or  3020  intercom button  3004  or  3006  is depressed at the base station  3000  while the telephone line is active on the base station  3000 , the active line is placed on hold and the selected handset alerts the user. If the user of that handset  3010  or  3020  then depresses the base station intercom button  3015  or  3025 , the intercom is initiated. When a handset intercom button  3016  or  3026  is depressed from another handset  3010  or  3020  while the telephone line is active on that handset, the active line is placed on hold and the selected handset  3010  or  3020  alerts the user. If the user then depresses handset intercom button  3016  or  3026  for handset  3010  or  3020  requesting the intercom, the intercom is initiated. When the intercom button is depressed from an inactive location requesting an intercom with an active location, the active location is alerted. If the active location then depresses the corresponding intercom button, the active line is placed on hold and the intercom initiated. When the intercom button from one inactive location is to another inactive location is depressed, whether a third location is active or not, the selected location alerts the user that an intercom is requested. If the user at that location depresses the corresponding intercom button, then the intercom is initiated between the two inactive locations without interfering with the active location. 
         [0067]      FIG. 6   a,    FIG. 6   b,  and  FIG. 6   c  illustrate the process flow of the base station  3000  of a multiple handset active call enabled cordless telephone with separate intercom buttons for each handset. 
         [0068]    If a base station  3000  intercom signal from handset  1   3010  is received by base station  3000 , as detected at processing segment  3100 , the base station  3000  checks if the telephone line is active on handset  1   3010  at processing segment  3101 . If the telephone line is active on handset  1   3010 , as detected at processing segment  3101 , the microprocessor  3005  disconnects the telephone line from transmitter/receiver circuit  1   3002  at segment  3102 , the active line is placed on hold, and the speaker/microphone  3008  is connected to transmitter/receiver circuit  1   3002  at segment  3103 , initiating the intercom communication between the base station  3000  and handset  1   3010 . 
         [0069]    If the telephone line is not active on handset  1   3010 , as detected at processing segment  3101 , the microprocessor  3005  checks if the telephone line is active at the base station  3000  at processing segment  3110 . If the telephone line is not active at the base station  3000 , as detected at processing segment  3110 , the microprocessor  3005  connects transmitter/receiver circuit  1   3002  to the speaker/microphone  3005  at segment  3112 , initiating the intercom communication between the base station  3000  and handset  1   3010 . 
         [0070]    If the telephone line is active at the base station  3000 , as detected at processing segment  3110 , the microprocessor  3005  sends a signal to the speaker/microphone  3007  to beep at segment  3113 , alerting the base station user that an intercom communication is requested. The microprocessor  3005  then checks if handset  1  intercom button  3004  was depressed at processing segment  3114 , indicating that the base station  3000  user wants to initiate the intercom communication. If handset  1  intercom button  3004  was depressed, as detected at processing segment  3114 , the microprocessor  3005  disconnects the telephone line from transmitter/receiver circuit  1   3002  at segment  3115 , the active line is placed on hold, and connects transmitter/receiver circuit  1   3002  to the speaker/microphone  3007  at segment  3116 , initiating the intercom communication between the base station  3000  and handset  1   3010 . 
         [0071]    If handset  1   3010  intercom button  3004  is not depressed, as detected at processing segment  3114 , the microprocessor  3005  checks if the base intercom signal from handset  1   3010  is received by base station  3000  at processing segment  3117 , indicating that the handset  1   3010  user no longer wants to initiate an intercom communication, i.e. the handset  1   3010  user pressed the base station  3000  intercom button  3015  a second time before the base station  3000  user pressed the handset  1   3010  intercom button  3004  to initiate the intercom communication. If the base intercom signal from handset  1   3010  was not received by base station  3000 , as detected at processing segment  3117 , the microprocessor  3005  returns to segment  3113 . If the base intercom signal from handset  1   3010  was received by base station  3000 , as detected at processing segment  3117 , the microprocessor  3005  returns to the start of base station processing. 
         [0072]    The same process is followed if a base station  3000  intercom signal from handset  2   3020  is received by base station  3000  at processing segment  3100  with transmitter/receiver circuit  2   3001  in place of transmitter/receiver circuit  1   3002 . 
         [0073]    After the intercom is initiated between the base station  3000  and handset  1   3010  at segments  3103 ,  3105 ,  3112 , and  3116 , the microprocessor  3005  checks if the speakerphone button  3008  was depressed at processing segment  3120  to determine if the intercom communication should be terminated. If the speakerphone button  3008  was depressed, as detected at processing segment  3120 , indicating that the base station  3000  user wants to terminate the intercom communication and activate the line, the microprocessor  3005  disconnects transmitter/receiver circuit  1   3002  from the speaker/microphone  3007  at segment  3121 , terminating the intercom communication, connects the telephone line and speaker/microphone  3007  at segment  3122 , activating the line, transmits the end of intercom signal to handset  1   3010  at segment  3123 , and proceeds the start of base station processing. 
         [0074]    If the speakerphone button  3008  is not depressed, as detected at processing segment  3120 , the microprocessor  3005  checks if handset  1  intercom button  3004  was depressed at processing segment  3124 , indicating that the base station  3000  user wants to terminate the intercom communication. If handset  1  intercom button  3004  was depressed, as detected at processing segment  3124 , the microprocessor  3005  disconnects transmitter/receiver circuit  1   3002  from the speaker/microphone  3007  at segment  3125 , terminating the intercom communication, transmits the end of intercom signal to handset  1   3010  at segment  3127  and proceeds to the start of base station processing. 
         [0075]    If handset  1  intercom button  3004  was not depressed, as detected at processing segment  3124 , the microprocessor  3005  checks if the activate line signal was received from handset  1   3010   1  at processing segment  3130 , indicating that the handset  1   3010  user wants to terminate the intercom communication and activate the line. If the base station activate line signal was received from handset  1   3010 , as detected at processing segment  3130 , the microprocessor  3005  disconnects the transmitter/receiver circuit  1   3002  from the speaker/microphone  3007  at segment  3131 , terminating the intercom communication, connects the phone line to transmitter/receiver circuit  1   3002  at segment  3132 , activating the line, and proceeds to the start of base station processing. 
         [0076]    If the activate line signal was not received from handset  1   3010 , as detected at processing segment  3130 , the microprocessor  3005  checks if the base station  3000  intercom signal from handset  1   3010  was received by base station  3000  at processing segment  3133 , indicating that the handset  1   3010  user wants to terminate the intercom communication. If the base station  3000  intercom signal from handset  1   3010  was received by base station  3000 , as detected at processing segment  3133 , the microprocessor  3005  disconnects the transmitter/receiver circuit  1   3002  from the speaker/microphone  3007  at segment  3134 , terminating the intercom communication, and proceeds to the start of base station processing. 
         [0077]    If the base station  3000  intercom signal from handset  1   3010  is not received by base station  3000 , as detected at processing segment  3133 , the microprocessor  3007  proceeds to processing segment  3120  to continue checking if the intercom communication should be terminated. 
         [0078]    If the base station  3000  does not receive a base intercom signal from either handset  1   3010  or handset  2   3020 , as detected at processing segment  3100 , the microprocessor  3007  checks if handset  2   3020  intercom signal from handset  1   3010  is received at processing segment  3200 . If handset  2   3020  intercom signal from handset  1   3010  is received, as detected at processing segment  3200 , the microprocessor  3005  checks if the telephone line is active on handset  1   3010  at processing segment  3201  as shown in  FIG. 6   b.  If the telephone line is active on handset  1   3010 , the microprocessor  3005  sends handset  1   3010  intercom signal to handset  2   3020  at segment  3202 , disconnects the telephone line from transmitter/receiver circuit  1   3002  at segment  3203 , the active line is placed on hold, and connects transmitter/receiver circuit  1   3002  to transmitter/receiver circuit  2   3001  at segment  3204 , initiating the intercom communication between handset  1   3010  and handset  2   3020 . 
         [0079]    If the telephone line is not active on handset  1   3010 , as detected at processing segment  3201 , the microprocessor  3005  checks if the telephone line is active at handset  2   3020  at processing segment  3210 . If the telephone line is active at handset  2   3020 , as detected at processing segment  3210 , then the microprocessor  3005  sends handset  1   3010  intercom signal to handset  2   3020  a segment  3211 . The processor then checks if handset  1   3010  intercom signal from handset  2   3020  is received at processing segment  3212 . If handset  1   3010  signal from handset  2   3020  is received, as detected at  3212 , the microprocessor  3005  disconnects transmitter/receiver circuit  2   3001  from the line at segment  3214 , the active line is placed on hold, and connects transmitter/receiver circuit  1   3002  and transmitter/receiver circuit  2   3001  at segment  3215 , initiating the intercom communication between handset  1   3010  and handset  2   3020 . 
         [0080]    If handset  1   3010  intercom signal from handset  2   3020  is not received by base station  3000 , as detected at processing segment  3212 , the microprocessor  3005  checks if handset  2   3020  intercom signal from handset  1   3010  was received. If handset  2   3020  intercom signal from handset  1   3010  was received by base station  3000 , then the microprocessor  3005  returns to processing segment  3100 . If handset  2   3020  intercom signal from handset  1   3010  was not received by base station  3000 , then the microprocessor  3005  returns to processing segment  3212 . 
         [0081]    If the telephone line is not active at handset  2   3020 , as detected at processing segment  3210 , then the microprocessor  3005  sends the handset  1   3010  intercom signal to handset  2   3020  at segment  3220 . The microprocessor  3005  then checks if the handset  1   3010  intercom signal from handset  2   3020  was received by base station  3000  at processing segment  3221 , indicating that the handset  2   3020  user wants to initiate an intercom communication with handset  1   3010 . If the handset  1   3010  intercom signal from handset  2   3020  was not received by base station  3000 , as detected at processing segment  3221 , the microprocessor  3005  checks if the handset  2   3020  intercom signal from handset  1   3010  was received by base station  3000  at processing segment  3226 , indicating that the handset  1   3010  user no longer wants to initiate an intercom communication with handset  2   3020 . If handset  2   3020  intercom signal from handset  1   3010  was not received by base station  3000 , as detected at processing segment  3226 , the microprocessor  3005  returns to processing segment  3221 . If the handset  2   3020  intercom signal from handset  1   3010  was received by base station  3000 , as detected at processing segment  3226 , the microprocessor  3005  returns to the start of base station processing. 
         [0082]    If handset  1   3010  intercom signal from handset  2   3020  was received by base station  3000 , as detected at processing segment  3221 , the microprocessor  3005  connects transmitter/receiver circuit  1   3002  to transmitter receiver  2  circuit  2   3001  at segment  3225 , initiating the intercom communication. 
         [0083]    Once the intercom communication is initiated at segments  3204 ,  3215 , and  3225 , the microprocessor  3005  determines if the intercom communication should be terminated. The microprocessor checks if the handset  1   3010  intercom signal from handset  2   3020  was received by base station  3000  at processing segment  3230 , indicating that the handset  1   3010  user wants to terminate the intercom communication. If it the handset  1   3010  intercom signal from handset  2   3020  was received by base station  3000 , as detected at processing segment  3230 , the microprocessor  3005  sends the handset  2   3020  intercom signal to handset  1   3010 , disconnects transmitter/receiver circuit  1   3002  from transmitter/receiver circuit  2   3001  at segment  3232 , terminating the intercom communication, and returns the start of base station processing. 
         [0084]    If the handset  1   3010  intercom signal from handset  2   3020  was not received by base station  3000 , as detected at processing segment  3230 , the microprocessor  3005  checks if the handset  2   3020  intercom signal from handset  1   3010  was received by base station  3000  at processing segment  3233 . If the handset  2   3020  intercom signal from handset  1   3010  was received by base station  3000 , as detected at processing segment  3233 , the microprocessor  3005  sends the handset  1   3010  intercom signal to handset  2   3020  at segment  3234 , disconnects transmitter/receiver circuit  1   3002  from transmitter/receiver circuit  2   3001  at segment  3232 , terminating the intercom communication, and proceeds the start of base station processing. 
         [0085]    If handset  2   3020  intercom signal from handset  1   3010  was not received by base station  3000 , as detected at processing segment  3233 , the microprocessor  3005  checks if the activate line signal was received from handset  1   3010  at processing segment  3240 . If the activate line signal from handset  1   3010  was received by base station  3000 , as detected at processing segment  3240 , the microprocessor  3005  sends handset  1   3010  intercom signal to handset  2   3020  at segment  3241 , disconnects transmitter/receiver circuit  1   3002  from transmitter/receiver circuit  2   3001  at segment  3242 , terminating the intercom communication, connects the telephone line to transmitter/receiver circuit  1   3002  at segment  3243 , activating the line on handset  1   3010 , and returns to the start of base station processing. 
         [0086]    If the activate line signal was not received from handset  1   3010 , as detected at processing segment  3240 , the microprocessor  3005  checks if the activate line signal was received from handset  2   3020  at processing segment  3244 . If the activate line signal was received from handset  2   3020 , as detected at processing segment  3244 , the microprocessor  3005  disconnects transmitter/receiver circuit  1   3002  from transmitter/receiver circuit  2   3001  at segment  3245 , terminating the intercom communication, connects the telephone line to transmitter/receiver circuit  2   3001  at segment  3246 , activating the line on handset  2   3020 , sends handset  2   3020  intercom signal to handset  1   3010  at segment  3247  and returns to the start of base station processing. 
         [0087]    If the activate line signal is not received from handset  2   3020 , as detected at processing segment  3244 , the microprocessor  3005  returns to processing segment  3230  to continue checking if the intercom communication should be terminated. 
         [0088]    If a the handset  2   3020  intercom signal from handset  1   3010  is not received by base station  3000 , as detected at processing segment  3200 , the base station  3000  checks if the handset  1   3010  intercom button  3004  or handset  2   3020  intercom button  3006  was pressed at processing segment  3300 . If the handset  1   3010  intercom button  3004  is pressed at processing segment  3300 , the microprocessor  3005  checks if the line is active at the base station  3000  at processing segment  3301 . If it the line is active, as detected at processing segment  3301 , the microprocessor  3005  disconnects the telephone line from the speaker/microphone  3007  at segment  3302 , the active line is placed on hold, sends a base station  3000  intercom signal to handset  1   3010  at segment  3303 , and connects the speaker/microphone  3007  to transmitter/receiver circuit  1   3002  at segment  3304  initiating the intercom communication. 
         [0089]    If the telephone line is not active at the base station  3000 , as detected at processing segment  3301 , the microprocessor  3005  checks if the telephone line is active on handset  1   3010  at processing segment  3305 . If the line is active at the base station, as detected at processing segment  3305 , the microprocessor  3005  sends a base station  3000  intercom signal to handset  1   3010  at segment  3306  and connects the speaker/microphone  3007  to transmitter/receiver circuit  1   3002  at segment  3307 , initiating the intercom communication between the base station  3000  and handset  1   3010 . 
         [0090]    If the telephone line is not active on handset  1   3010 , as detected at processing segment  3305 , the microprocessor sends the base station  3000  intercom signal to handset  1   3010  at segment  3311  and checks if the base station  3000  intercom signal from handset  1   3010  was received by base station  3000  at processing segment  3312 , indicating that the handset  1   3010  user wants to initiate the intercom communication. If the base intercom signal from handset  1   3010  was not received by base station  3000 , as detected at processing segment  3312 , the microprocessor  3005  checks if the handset  1   3010  intercom button  3004  was pressed at processing segment  3313 , indicating that the base station  3000  user no longer wants to initiate the intercom communication. If the handset  1   3010  intercom button was not depressed, as detected at processing segment  3313 , the microprocessor  3005  returns to processing segment  3312  to continue the loop until the intercom communication is initiated or the intercom communication is cancelled. 
         [0091]    If the base intercom signal from handset  1   3010  is received by base station  3000  at processing segment  3312 , the microprocessor  3005  disconnects the telephone line from transmitter/receiver circuit  1   3002  at segment  3314 , the active line is placed on hold, and connects the speaker/microphone  3007  to transmitter/receiver circuit  1   3002  at segment  3315 , initiating the intercom communication. 
         [0092]    After the intercom communication is initiated between the base station  3000  and handset  1   3010  at segments  3304 ,  3307 , and  3315 , the microprocessor  3005  determines if the intercom communication should be terminated. The microprocessor  3005  checks if the handset  1   3010  intercom button  3004  was pressed at processing segment  3316 . If the handset  1   3010  intercom button  3004  was pressed, as detected at processing segment  3316 , the microprocessor  3005  sends the base station  3000  intercom signal to handset  1   3010  at segment  3317 , disconnects transmitter/receiver circuit  1   3002  from the speaker/microphone  3007  at segment  3318 , terminating the intercom communication, and returns to the start of base station processing. 
         [0093]    If the handset  1   3010  intercom button  3004  was not pressed, as detected at processing segment  3316 , the microprocessor  3005  checks if the base station  3000  intercom signal from handset  1   3010  was received by base station  3000  at processing segment  3320 . If the base station  3000  intercom signal from handset  1   3010  was received by base station  3000 , as detected at processing segment  3320 , the microprocessor  3005  disconnects transmitter/receiver circuit  1   3002  from speaker/microphone  3007 , terminating the intercom communication, and proceeds to the start of base station processing. 
         [0094]    If the base station  3000  intercom signal from handset  1   3010  was not received by base station  3000 , as detected at processing segment  3320 , the microprocessor  3005  checks if the activate line signal was received from handset  1   3010  at processing segment  3321 . If the activate line signal was received from handset  1   3010 , as detected at processing segment  3321 , the microprocessor  3005  disconnects the transmitter/receiver circuit  1   3002  from the speaker/microphone  3007  at segment  3322 , terminating the intercom communication, connects the telephone line to transmitter/receiver circuit  1   3002  at segment  3323 , activating the line on handset  1   3010 , and returns to the start of base station processing. 
         [0095]    If the activate line signal was not received from handset  1   3010 , as detected at processing segment  3321 , the microprocessor  3005  checks if the activate line button  3008  was depressed at processing segment  3330 . If the activate line button  3008  was depressed, as detected at processing segment  3330 , the microprocessor  3005  sends the base intercom signal to handset  1   3010  at segment  3331 , disconnects transmitter/receiver circuit  1   3002  from the speaker/microphone  3007  at segment  3332 , terminating the intercom communication, connects the telephone line to the speaker/microphone  3007  at segment  3333 , activating the line at the base station  3000 , and returns to the start of base station processing. 
         [0096]    If the activate line button  3008  was not depressed, as detected at processing segment  3330 , the microprocessor  3005  returns to processing segment  3316  to continue the loop until the intercom communication should be terminated. 
         [0097]      FIG. 6   d  and  FIG. 6   e  illustrate the process flow of a handset  3010   3020  for a multiple handset active call enabled cordless telephone with separate intercom buttons for each handset. 
         [0098]    When the handset  2   3020  intercom button  3016  is pressed on handset  1   3010 , as detected at processing segment  3400 , the microprocessor  3013  sends the handset  2   3020  intercom signal to the base station  3000  at segment  3401  and checks if the telephone line is active on handset  1   3010  at processing segment  3402 . If the telephone line is inactive on handset  1   3010 , the microprocessor  3013  connects transmitter/receiver circuit  3011  to the speaker/microphone  3012   3022  at segment  3403 , initiating the intercom communication between handset  1   3010  and handset  2   3020 . 
         [0099]    If the handset  2   3020  intercom button  3016  is not pressed, as detected at processing segment  3400 , the microprocessor  3013  checks if the handset  2   3020  intercom signal from base station  3000  was received by handset  1   3010  at processing segment  3410 , indicating that the handset  2   3020  user wants to initiate an intercom communication with handset  1   3010 . If the handset  2   3020  intercom signal from base station  3000  was received by handset  1   3010 , as detected at processing segment  3410 , the microprocessor  3013  sends a signal to the speaker/microphone  3012  to beep at segment  3411  and checks if the handset  2   3020  intercom button  3016  was depressed at processing segment  3412 , indicating that the handset  1   3010  user wants to initiate the intercom communication with handset  2   3020 . If the handset  2   3020  intercom button  3016  was not depressed, as detected at processing segment  3412 , the microprocessor  3013  checks if the handset  2   3010  intercom signal from base station  3000  was received by handset  1   3010  at processing segment  3413 , indicating that the handset  2   3020  user no longer wants to initiate an intercom communication. 
         [0100]    If the handset  2   3020  intercom signal from base station  3000  was received by handset  1   3010 , as detected at processing segment  3413 , then the microprocessor  3013  returns to the start of handset  1  processing. If the handset  2   3020  was not received, then the microprocessor  3013  returns to segment  3411 . 
         [0101]    If the handset  2   3020  intercom button  3016  was depressed, as detected at processing segment  3412 , the microprocessor  3013  sends the handset  2   3020  intercom signal at segment  3414  and checks if the telephone line is active on handset  1   3010  at processing segment  3415 . If the telephone line is not active on handset  1   3010 , as detected at processing segment  3415 , the microprocessor  3013  connects transmitter/receiver circuit  3011  to the speaker/microphone  3012  at segment  3416 , initiating the intercom communication. 
         [0102]    After the intercom communication is initiated between handset  1   3010  and handset  2   3020  at segments  3403 ,  3416 ,  3402  and  3415 , the microprocessor  3013  determines if the intercom communication should be terminated. The microprocessor  3013  checks if the handset  2   3020  intercom button  3016  was depressed at processing segment  3430 , indicating that the handset  1   3010  user wants to terminate the intercom communication. If the handset  2   3020  intercom button  3016  was depressed, as detected a processing segment  3430 , the microprocessor  3013  transmits the handset  2  intercom signal to the base station at segment  3431 , disconnects the transmitter/receiver circuit  3011  from the speaker/microphone  3012  at segment  3432 , terminating the intercom communication, and returns the start of handset  1  processing. 
         [0103]    If the handset  2   3020  intercom button  3016  is not depressed, as detected at processing segment  3430 , the microprocessor  3013  checks if the handset  2   3020  intercom signal was received from base station  3000  by handset  3000  at processing segment  3433 . If the handset  2   3020  intercom signal from base station  3000  was received by handset  3010 , as detected at processing segment  3433 , the microprocessor  3013  disconnects transmitter/receiver circuit  3011  from the speaker/microphone  3012  at segment  3434 , terminating the intercom communication, and returns to the start of handset  1  processing. If the handset  2   3020  intercom signal from base station  3000  was not received by handset  1   3010  at processing segment  3433 , the microprocessor  3013  returns to processing segment  3430  to continue the loop until the intercom communication between handset  1   3010  and handset  2   3020  should be terminated. 
         [0104]    If the handset  2  intercom signal from base station  3010  is not received by handset  1   3010 , as detected at processing segment  3410 , the microprocessor  3013  checks if the base station  3000  intercom button  3015  was depressed at processing segment  3420 , indicating that the handset  1   3010  user wants to initiate an intercom communication with the base station  3000 . If the base station  3000  intercom button  3015  was depressed, as detected at processing segment  3420 , the microprocessor  3013  sends the base station  3000  intercom signal at segment  3421  and checks if the telephone line is active on handset  1   3010  at processing segment  3422 . If the telephone line is not active at handset  1   3010 , as detected at processing segment  3422 , the microprocessor  3013  connects the transmitter/receiver circuit  3011  to the speaker/microphone  3012  at segment  3423 , initiating the intercom communication. 
         [0105]    If the base station intercom button  3015  was not depressed, as detected at processing segment  3420 , the microprocessor  3013  checks if the base station  3000  intercom signal from base station  3000  was received by handset  1   3010  at processing segment  3500 , indicating that the base station  3000  user wants to initiate an intercom communication with handset  1   3010 . If the base station  3000  intercom signal from base station  3000  was not received by handset  1   3010 , as detected at processing segment  3500 , the microprocessor  3013  returns to the start of handset  1  processing. 
         [0106]    If the base station  3000  intercom signal from base station  3000  was received by handset  3010 , as detected at processing segment  3500 , the microprocessor  3013  sends a signal to the speaker/microphone  3012  to beep and checks if the base station  3000  intercom button  3015  was depressed at processing segment  3502 . If the base station  3000  intercom button  3015  was not depressed, as detected at processing segment  3502 , the microprocessor  3013  checks if the base station intercom signal from base station  3000  was received by handset  3010  at processing segment  3506 , indicating that the base station  3000  user no longer wants to initiate an intercom communication. If the base station  3000  intercom signal from base station  3000  was not received by handset  3010 , as detected at processing segment  3506 , the microprocessor  3013  returns to segment  3501  to continue the loop until the base station  3000  user cancels the request to initiate an intercom communication or the handset  1   3010  user initiates the intercom communication. If the base station  3000  intercom signal from base station  3000  was received by handset  3010 , as detected at processing segment  3506 , indicating that the base station  3000  user no longer wants to initiate an intercom communication, the microprocessor  3013  returns to the start of handset  1  processing. 
         [0107]    If the base station  3000  intercom button  3015  was depressed, as detected at processing segment  3502 , the microprocessor  3013  transmits the base station intercom signal to the base station  3000  at segment  3503  and check if the telephone line is active on handset  1   3010  at processing segment  3504 . If the telephone line is not active, as detected at processing segment  3504 , the microprocessor  3013  connects the transmitter/receiver circuit  3011  to the speaker/microphone  3012  at segment  3505 , initiating the intercom communication. 
         [0108]    After the intercom communication is initiated at segments  3423 ,  3505 ,  3422  and  3504 , the microprocessor  3013  determines if the intercom communication between the base station  3000  and handset  1   3010  should be terminated. The microprocessor  3013  checks if the base station  3000  intercom button  3015  was depressed at processing segment  3510 , indicating that the handset  1   3010  user wants to terminate the intercom communication. If the base station  3000  intercom button  3015  was depressed, as detected at processing segment  3510 , the microprocessor  3013  transmits the base station  3000  intercom signal to the base station  3000  at segment  3511 , disconnects the transmitter/receiver circuit  3011  from the speaker/microphone  3012  at segment  3512 , terminating the intercom communication and returns the start of handset  1  processing. 
         [0109]    If the base station  3000  intercom button  3015  was not depressed, as detected as processing segment  3510 , the microprocessor  3013  checks if the base station  3000  intercom signal from base station  3000  was received by handset  3010  at processing segment  3513 . If the base station  3000  intercom signal from base station  3000  was not received by handset  3010 , as detected at processing segment  3513 , the microprocessor  3013  returns to processing segment  3510  to continue the loop until the intercom communication between the base station  3000  and handset  1   3010  should be terminated. 
         [0110]    If the base station  3000  intercom communication was received, as detected at processing segment  3513 , the microprocessor  3013  disconnects transmitter/receiver circuit  3011  from the speaker/microphone  3012  at segment  3514 , terminating the intercom communication, and returns the start of handset  1  processing. 
         [0111]    Accordingly, no matter which of the base station  3000 , handset  1   3010 , or handset  2   3020  initiates an intercom communication during an active call, the active call is placed on hold during the intercom communication and is resumed when the intercom communication is over. 
         [0112]    While the above embodiments of the present invention is described using a microprocessor as a control circuit for the base station and the handsets, the functions of each can be achieved using other control circuits which may be implemented as an ASIC or other digital or analog control circuit. 
         [0113]    While various specific embodiments of the invention have been described and illustrated, these are only exemplary of the invention and many modifications and substitutions can be made without departing from the spirit or scope of the invention. Accordingly, the invention is not limited by the foregoing description, but is only limited by the scope of the appended claims.