Abstract:
A method of interrupting a call between two parties in a switched telecommunications. A monitoring switch monitors the call for a party initiated interrupt signal. Whenever the monitoring switch receives an interrupt signal initiated by its associated party, the monitoring switch initiates a call between the party initiating the interrupt signal and a serving platform, and parks the other party at a port of the monitoring switch. The monitoring switch then monitors the status of the call between the party initiating the interrupt signal and the serving platform, and the status of the parked call so that the parties may be reconnected at the conclusion of the call between the requesting party and the serving platform or informed if one of the parties disconnects before they are reconnected.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to telephone call processing, and more particularly to a method of providing party initiated call interruption services in a switched telecommunications network, such as a long distance telephone network. 
     DESCRIPTION OF THE PRIOR ART 
     Private telephone systems and local telephone companies currently provide services that allow a caller to interrupt a call in progress. For example, local telephone companies provide Call Waiting service that alerts a caller with a special tone that there is an incoming call waiting for the caller. When the caller hears the special tone, the caller may take the incoming call by pressing and releasing the switch hook. Pressing and releasing the switch hook puts the first call affectively on hold and connects the caller to the incoming call. The caller can toggle back and forth between the original call and the incoming call by pressing and releasing the switch hook. 
     Another example of mid-call interruption services provided by local telephone companies is three-way calling, which allows a caller to be connected to two different parties at the same time. During a call to a first party, a caller can put that party on hold by pressing and releasing the switch hook. When the caller receives a dial tone, the caller can dial the number of the other party. When the other party answers, the caller and the other party can talk privately or the caller can add the first party into the conversation by pressing and releasing the switch hook. If either of the other parties disconnects, the conversation continues with the remaining party. When the caller hangs up, all other parties are disconnected. 
     Currently, there is no system by which long distance telephone carriers can provide mid-call interruption services. It is therefore an object of the present invention to provide a system for interrupting calls between two parties in a switched telecommunications network, such as a long distance telephone network. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method of interrupting an original call between two parties in a switched telecommunications network in which each of the parties is associated with a switch of the network. A switch monitors the call for a party initiated interrupt signal, which is a dual tone multi-frequency (DTMF) sequence. Whenever the monitoring switch receives an interrupt signal, the monitoring switch initiates a new call between the party initiating the interrupt signal and a serving platform, and parks the other party to the original call at a port of the monitoring switch. The monitoring switch then monitors the status of the new call between the party initiating the interrupt signal and the serving platform, and the status of the parked original call. 
     Whenever the serving platform releases the requesting party, the monitoring switch determines whether or not the parked party is still connected. If the parked party is still connected, the switch reconnects the requesting party and the parked party. If the parked party is disconnected, then the monitoring switch informs the requesting party that the parked party has disconnected, and releases the original call to the parked party. 
     Whenever the requesting party disconnects, the switch determines whether or not the parked party is still connected. If the parked party is still connected, the monitoring switch informs the parked party that the requesting party has disconnected and releases the call to the parked party. Whenever the parked party disconnects, the monitoring switch determines whether or not the requesting party is still connected. If the requesting party is still connected, the monitoring switch waits until the serving platform releases the requesting party and then informs the requesting party that the parked party has disconnected. 
     The method of the present invention is preferably implemented with a call park table at the monitoring switch. When the monitoring switch initiates the call to the serving platform, the monitoring switch inserts in the call park table an identifier identifying the original call between the parties, an identifier identifying the new call between the requesting party and the serving platform, and an action code that identifies the status of the parked call. 
     When the monitoring switch receives a release message, the monitoring switch searches the call park table for a match between the identifier of the released call and the identifier of the original call between the parties or the identifier of the new call between the requesting party and the serving platform. If there is no match, the monitoring switch processes the release message in the normal way. Whenever the identifier of the released call matches the identifier of the new call between the requesting party and the serving platform, the monitoring switch checks the action code to determine whether or not the parked party is still connected. Whenever the parked party is still connected, the monitoring switch reconnects the requesting party and the parked party. Whenever the parked party is not still connected, the monitoring switch applies a call treatment informing the requesting party that the parked party has disconnected. 
     Private telephone systems and local telephone companies currently provide services that allow a caller to interrupt a call in progress. For example, local telephone companies provide Call Waiting service that alerts a caller with a special tone that there is an incoming call waiting for the caller. When the caller hears the special tone, the caller may take the incoming call by pressing and releasing the switch hook. Pressing and releasing the switch hook puts the first call effectively on hold and connects the caller to the incoming call. The caller can toggle back and forth between the original call and the incoming call by pressing and releasing the switch hook. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram illustrating a preferred embodiment of the system of the present invention. 
     FIGS. 2A and 2B comprise a flowchart of a preferred implementation of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and first to FIG. 1, a long distance telephone network is designated generally by the numeral  11 . Long distance telephone network  11  includes a plurality of physically interconnected switches, including a first switch  13  and a second switch  15 . Long distance telephone network  11  also includes a network control system (NCS)  17  that communicates with the switches of network  11  by suitable data links. 
     NCS  17  provides system management services to network  11 . For example, NCS  17  can receive requests for routing instructions from the switches of network  11  and, in response to such requests provide routing instructions. NCS  17  also monitors and collects system performance data. Additionally, NCS  17  can provide restoration services in the event of the failure of a physical link between switches of network  11 . 
     Network  11  also includes one or more serving platforms, including a serving platform  19 . Serving platform  19  is physically connected to the switches of network  11  either directly or through intermediate switches. Serving platform  19  provides services such as conference calling, operator assistance, stock quotes, etc., according to the present invention. 
     Long distance telephone network  11  is adapted to transport long distance telephone calls between customers connected to local exchange carriers (LECs). For example, in FIG. 1, a first caller  21  is a customer of a first LEC  23 , and a second caller  25  is a customer of a second LEC  27 . If first caller  21  desires to place a long distance call to second caller  25 , and first caller  21  is a customer of network  11 , LEC  23  connects first caller  21  to first switch  13  of network  11 . First switch  13  routes the call, either directly or indirectly through intermediate switches, to second switch  15 , which routes the call to second caller  25  through LEC  27 . 
     Call setup between first switch  13  and second switch  15  is preferably accomplished using the signalling system  7  (SS 7 ) protocol. First switch  13  sends second switch  15  an initial address message (IAM) that, among other things, identifies the called party and assigns to the call a network call identifier (NCID). After the call between first party  21  and second party  25  is set up, the parties are connected until the call is terminated or interrupted. 
     According to the present invention, either caller  21  or second caller  25  can initiate interruption of their call. For example, in FIG. 1, first caller  21  may wish to access features such as conference calling, operator services, or stock quotes. According to the present invention, first caller  21  initiates an interrupt signal, which is a dual tone multi-frequency (DTMF) sequence. For example, the interrupt signal may be the DTMF sequence “12##.” The ## sequence identifies the sequence as an interrupt signal and the preceding digits identify the type of services requested. 
     In the present invention, switch  13  monitors the call between first caller  21  and second caller  25  for party initiated party interrupt signals. When switch  13  detects an appropriate sequence of DTMF tones, it captures them and sends them to NCS  17  in an application data field (ADF) routing request message. NCS  17  responds to switch  13  with an ADF routing response, which contains routing instructions for establishing a new call to a serving platform  19 . Upon receipt of routing instructions, the original call-between the parties is parked at switch  13  and a new call is initiated from switch  13  to serving platform  19 . The new call is initiated with an IAM message that includes a network call identifier (NCID) that identifies the new call. The IAM message also includes the NCID of the original call so that the serving platform can identify the call for services requiring communication with the parked caller. The original call is parked at a port on the network side of switch  13  and first caller  21  is no longer connected to second caller  25 . However, the original call between the parties remains in a billable state while second caller  25  is parked. A recorded announcement or music may be played to first caller  25  for the duration of the parked period. 
     After the new call is established and the original call is parked, switch  13  monitors the status of both the original call and the new call. In the event that a call leg is released or disconnected, switch  13  must take appropriate action. For example, if second caller  25  hangs up while the new call between first caller  21  and serving platform  19  is in progress, switch  13  must notify first caller  21  at the conclusion of the new call that second caller  25  has disconnected. Similarly, if first caller  21  hangs up before the completion of the new call, first switch  13  must notify second caller  25  that first caller  21  has disconnected. Finally, if serving platform  19  releases the new call, then, if the original call is still parked, i.e., first caller  25  has not disconnected, first switch  13  must reconnect first caller  21  and second caller  25  so that they may resume the original call. 
     Processing at a monitoring switch, which in the example of FIG. 1 is switch  13 , may be best understood with reference to the flowchart of FIGS. 2A and 2B. Referring first to FIG. 2A, the parties are in conversation as indicated generally at block  31 . During the conversation, the monitoring switch waits for a party initiated interrupt signal, which in the preferred embodiment is a DTMF sequence. If, at decision block  33 , the switch detects an appropriate DTMF sequence, the switch requests routing instructions from the network control system at block  35 . When, at decision block  37 , routing instructions are received, the switch routes the requesting party to a serving platform in accordance with the routing instructions and opens a billing record for the new call, at block  39 . Additionally, the switch parks the nonrequesting party at block  41  and populates a call park table with certain information to identify and keep track of the parked original call and the new call, at block  43 . 
     The call park table enables the switch, when it receives a release message, to determine whether or not a parked call is involved and, if so, what action to take. The call park table contains, for each parked call, the NCID of the new call, the NCID of the parked original call, and an action code, which identifies the status of the parked call. The NCID of the parked original call contains, among other things, the number of the port of the monitoring switch where the parked call is parked. In the preferred embodiment, the action code has two values, in which a first value denoted “0” indicates that the parked call is connected and a second value “1” indicates that the parked call is disconnected. The value of the action code is set to 1 when the call park table is populated. 
     After the switch has populated the call park table at block  43 , the switch waits for a release message, at block  45 , and performs release processing, indicated generally at block  47  and shown in detail in FIG.  2 B. 
     Referring now to FIG. 2B, there is shown processing of a release message. The switch may be handling hundreds of calls simultaneously, so it typically receives release messages frequently. However, according to the present invention, the switch may receive a release message from serving platform  19  at the completion of the new call, or from second switch  15  if parked caller  25  disconnects, or from LEC  23  if requesting caller  21  disconnects. 
     A release message includes the NCID of the released call. Accordingly, the switch checks the call park table, at block  51 , to determine whether or not there is a match between the NCID of the released call and the NCID of the new call or the NCID of the parked original call. If, at decision block  53 , there is no match, then the switch performs normal processing of the released call, at block  55 , and returns to block  45  of FIG.  2 A. 
     If, at decision block  53 , there is a match, the system test, at decision block  57 , whether or not the NCID in the release message matches the new NCID. If so, the switch tests, at decision block  59 , whether or not the action code in the call park table equals “1”, which indicates that the parked party has disconnected. If not, the switch reconnects the callers and closes the billing record for the new call, at block  61 . Then the switch clears the call park table entries for the original call at block  63 . If, at decision block  59 , the action code equals “1”, which indicates that the parked party has disconnected, the switch delivers an announcement informing the requesting party that the parked party has disconnected, at block  65 . Then the switch disconnects the requesting caller, at block  67 , closes the billing records for the new and original calls, at block  69 , and clears the call park table, at block  63 . 
     If, at decision block  57 , the NCID in the release message does not match the new NCID, which means that the NCID in the release message matches the NCID of the original call, the switch tests, at decision block  71 , whether the release message is from the original party. If so, the switch tests, at decision block  73 , whether or not the action code in the call park table equals “1”, indicates that the parked party has disconnected. If not, the switch delivers an announcement informing the parked party that the original party has disconnected, at block  75 . Then the switch releases both the new and original calls, at block  77 , closes the billing records for the new and original calls, at block  69 , and clears the call park table, at block  63 . If, at decision block  73 , the action code indicates that the parked party has already disconnected, the switch releases the serving platform, at block  79 , closes the billing records for the new and original calls, at block  69 , and clears the call park table, at block  63 . 
     If, at decision block  71 , the release message is not from the original party, which indicates that the parked caller has disconnected, the switch updates the call park table with a new action code equal to “1”, at block  79 , and returns to block  45  of FIG. 2A to wait for a release message from either the serving platform or the original party. If the serving platform disconnects, the release message will contain the new NCID, at decision block  57 , and the action code will be “1”, at decision block  59 . Accordingly, the switch will inform the requesting party that the parked party has disconnected, at block  65 , and complete processing of the call. If the requesting party disconnects, the release message will contain the original NCID, at decision block  57 , and the action code will be “1”, at decision block  73 . Then, the switch will release the serving platform, at block  79 , and complete processing of the call. 
     From the foregoing, those skilled in the art will recognize that the present invention provides call interrupt services in a switched telephone network. One party to a call is parked at a monitoring switch while the other party is connected to a serving platform. The monitoring switch maintains the status of both the parked call and the new call between the original party and the serving platform with a call park table. The monitoring switch processes release messages according information contained in the call park table.