Abstract:
Apparatus and a method for providing accurate caller identification to a called party. If a call is transferred to a called party, the called party receives the identification of the caller, not of the intermediate station. Advantageously, the caller is identified to the called party, even if the call is transferred.

Description:
TECHNICAL FIELD 
     This invention relates to automatic calling line identification in telecommunications systems. 
     PROBLEM 
     Calling line identification is a very popular service. It allows the user of the service to identify the caller and to either be prepared to talk to that caller, or to ignore the call. 
     In recent years, calling line identification has been further enhanced by providing the name of the owner of the telephone line or mobile station that is making a call. Thus, the called party need not be able to recognize the caller&#39;s telephone number, but can simply see the caller&#39;s name. 
     A problem with presently available calling line identification is that if the call has been transferred, the identification that the called party receives is the identification of the line and name of the party from which the call was transferred. 
     SOLUTION 
     Applicants have further analyzed this problem and have recognized that the ideal solution is to provide the original caller&#39;s identification to a called party, i.e., to any station that is alerted for the call. 
     Applicants have solved the above problem and have made a contribution over the teachings of the prior art in accordance with their invention, wherein if a call is transferred from another line, the called party sees a calling line identification display or hears a calling line identification announcement that corresponds to the original caller&#39;s identification, not to the identification of the line from which a call was transferred. For calls that are transferred, the original calling line identification, possibly enhanced by the name associated with the caller&#39;s telephone number, is retained by the transferring switch and is inserted into the calling line identification field of the signaling message between the transferring switch and the terminating switch. The terminating switch will then send or announce to the called party the telephone number and/or name of the caller as received in the signaling message, not the name and/or telephone number of the transferring party. 
     In accordance with one aspect of Applicants&#39; invention, for customers having a transfer feature or three-way calling feature, when a call to such customer is made, the switching system serving that customer retains the caller&#39;s identification. Subsequently, if the called party transfers the call to a third party, the signaling message (for inter-office calls) or the calling line identification message, uses the retained information, not information associated with the party which originally answered the call. The basic principle, that on all transferred calls, the calling lines identification information is retained in the calling line identification field of the signaling message, makes implementation of this feature a straightforward process. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING(S) 
     FIG. 1 is a block diagram illustrating Applicants&#39; invention; and 
     FIGS. 2-4 are flow diagrams illustrating the method of Applicants&#39; invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 is a block diagram illustrating Applicants&#39; invention. A caller station  101  connected to an originating switch  103 , originates a call. The originating switch optionally consults a database  105  to determine the name associated with the caller&#39;s telephone number. For an inter-office call, a common channel signaling message  111  is sent to the switch specified by the original called number, i.e., the number dialed or specified, (e.g., via speed calling), by the caller station. (All messages shown herein include only those fields which pertain to the invention; many other fields are required for controlling all other actions required for establishing connections in a network.) The message  111  transmitted to the first terminating switch  121  includes the original called number  113 , the calling number  115 , and the calling name  117 . The first terminating switch  121  sends message  131  to the transferring line  122 . Message  131  includes the original calling number  133 , and calling name  135 . 
     First terminating switch  121  retains the calling number  115  and the calling name  117  of the initial address message  111 , if the original called number has a call transfer feature. 
     If a call is to be transferred, it may be transferred to an intra-office called terminal  123 , or an inter-office called terminal  125 . If the call is being transferred to terminal  123 , then message  126 , including calling number  127  and calling name  129 , is sent along with the alerting signal from terminating switch  121  to called terminal  123 . If the call is being transferred to an inter-office called terminal  125 , then message  151  is prepared in first terminating switch  121 . The inter-office call set-up message  151  includes the calling number  153 , the calling name  155 , original called number  157  (needed for call set-up purposes), and the transferred-to called number  158 , (also needed for call set-up purposes). A call transfer indicator  159  is also provided in the message. The second terminating switch  161  receives this message and sets up a connection to called terminal  125 . It sends to that terminal, a calling number identification message  163 , including the intended calling number  165 , and the intended calling name  167 . Optionally, the message can include a transfer indicator for display at the called terminal. 
     One other situation in which it is desirable to provide a different calling number identification than is provided in the prior art, is a transfer wherein the originator causes a connection to be established between the called party and a third party. Caller  101  originally requests that a call be set up to station  122 . After talking to the user of station  122 , the caller at station  101  recognizes that the call should be transferred to a third party so that station  122  is connected, for example, to station  125 , and station  101  is no longer connected to the call. In response to a request from station  101 , switch  103  generates message  170  for transmission to switch  121 . Message  170  includes the identity of the requesting number  171  and original called number  172 , and called name  173 , to identify the call. Message  170  also includes the identity  174  of the third party, and an indication  175  of the type of transfer requested. Message  163  will then be sent to terminal  125 , including the identity of station  122  which, from the point of view of station  125 , is the true “calling party”. 
     FIG. 2 is a flow diagram illustrating the operation of Applicants&#39; invention. The originating switch, (switch  103 ), receives an outgoing call, (Action Block  201 ). The originating switch transmits the call to a switching system for serving the called number, (Action Block  203 ). At the receiving end of this message, i.e., first terminating switch  121 , a connection is established to the called station, (Action Block  205 ). 
     While the call is being established, Test  207  is performed to determine whether the called station has a transfer feature, aand whether the original calling party has permitted its number/name to be presented. If the called station does have a transfer feature and the calling party has permitted its number/name to be presented, then the original calling number and name are saved, (Action Block  209 ). Otherwise, the actions of the prior art are performed, (Action Block  211 ). 
     Test  301  (FIG. 3) determines whether the called party invokes call transfer. If not, then the actions of the prior art are performed, (Action Block  303 ). If the called station does invoke a call transfer feature, then Test  305  is used to determine whether the destination of the transferred call is in the same switching system. If the transferred-to station is in the same switching system, then the saved caller identification data is transmitted to the transferred-to station, (Action Block  307 ), and the call connection is established to the transferred-to station, (Action Block  309 ). 
     If the result of Test  305  indicates that the transferred-to terminal is not on the first terminating switch, then a message is prepared for the second terminating switch, the message including the caller&#39;s number and name, (Action Block  311 ). The call is received in the second intermediate switch with an indication that the call has been transferred, (Action Block  313 ). The transferred call is established, (Action Block  315 ), and the original caller&#39;s number and name is transmitted to the called station&#39;s caller identification box, (Action Block  317 ). 
     In an alternative embodiment, the transferring switch can request the original caller&#39;s identification data when a call transfer request is detected. This arrangement avoids the necessity for storing this data in the transferring switch, but may increase call set-up time. 
     FIG. 4 illustrates the actions performed when a caller causes a connection to be established between a called party and a third party. The switch of the caller receives a request to establish such a connection, (Action Block  401 ). That switch then transmits a request to the switch serving the original called party, (Action Block  403 ). The switch serving the third party sends a caller identification message to the third party, the message specifying the identification of the original called party, (Action Block  405 ). A connection is established between the original called party and the third party, (Action Block  407 ), and the original caller is disconnected from the call. 
     The above description is of one preferred embodiment of Applicants&#39; invention. Other embodiments will be apparent to those of ordinary skill in the art, without departing from the scope of this invention. The invention is limited only by the attached claims.