Voice messaging system with ability to prevent hung calls

Telephonic communications – Audio message storage – retrieval – or synthesis

Reexamination Certificate

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Details

C379S081000, C379S088070, C379S088130, C379S088200, C379S088210, C379S088250

Reexamination Certificate

active

06608887

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to voice messaging systems, and more particularly to a multiple node messaging system wherein each Network Interface Unit or Telephony Services Platform (which is a form of Network Interface Unit) is shared by two or more host computers. Still more particularly, the present invention concerns a voice messaging system including a mechanism for preventing channels from being hung so completely that they can not be recovered. The invention also prevents cross connection of calls such that a customer using a given channel can find himself listening to someone else's call.
BACKGROUND OF THE INVENTION
Messaging systems that provide voice, fax and/or e-mail messaging capabilities are well known.
FIG. 1
illustrates an exemplary prior art messaging system developed by Unisys Corporation, Blue Bell, Pa., the assignee of the present invention. The system of
FIG. 1
comprises multiple servers (which may be implemented, e.g., with A-series or Clearpath™ computers offered by Unisys Corporation) each supporting a network applications platform (NAP), which provides an underlying platform for storage and retrieval of messages, and a messaging application running on the platform. A voice mail application, such as the Unisys Universal Voice Messaging System (UVMS), is an example of a messaging application that runs on the messaging platform. The UVMS application determines how calls to the messaging system are handled, what prompts are played to callers, and which features are available. Such applications typically maintain a database of subscribers who have “mailboxes” on the system. The messaging platform interfaces to a telephone network through a Network Interface Unit (NIU). Received messages are stored by the messaging platform in a local message store, or voice file.
The network applications platform, or NAP, may be located at a local telephone company connected to one or more central offices or switches, or could alternatively be located on the premises of a customer, such as a large or medium-sized company. In the latter case, the NAP would typically be connected to a private branch exchange (PBX) instead of directly to a PSTN. Telephone customers typically demand high (close to 100%) system availability, which means that, for a large customer having hundreds or even thousands of employees at a given location, it is extremely difficult to take the telephony application off-line for even a short time to make updates or modifications. Therefore, when it becomes necessary to modify the application in any way, the application provider needs a way to make such modifications in a way that maintains system availability. This need is particularly severe for high volume telephony systems, which typically cannot be taken out of service without inconveniencing significant numbers of users.
Network Interface Units are available from a number of different vendors. For example, NIUs suitable for use with the present invention include: (a) the Telephony Services Platform available from Unisys Corporation, Blue Bell, Pa.; (b) the Summa Four VCO 80 available from Summa Four, Inc., Manchester, N.H.; and (c) the Voice Frame 2020 available from Harris Corporation, Melbourne, Fla. The Telephony Services Platform (TSP) is most preferred. The difference between it and the other products just mentioned is that the TSP includes a board that plays back digitized voice from a voice file whereas the other products require a separate playback module.
In use, if a subscriber is not available when an incoming call is received, the Public Switched Telephone Network (PSTN) forwards the call to the messaging system, which typically allows the caller to record a message, and then will store the message for later retrieval by the subscriber. A key (or token) returned to the messaging application uniquely identifies the stored message data within the message store. This key can be used at a later time to retrieve the message from the message store for playback to the subscriber.
In the exemplary system shown in
FIG. 1
, a first node of the system comprises a server/NAP
10
a
, voice file and database
12
a
and NIU
14
a
. Similarly, a second node comprises a server/NAP
10
b
, voice file and database
12
b
and NIU
14
b
; and a third node comprises a server/NAP
10
c
, voice file and database
12
c
and NIU
14
c
. The first node, e.g., could be responsible for a predefined geographic area encompassing hundreds of thousands of subscribers, or simply for a predefined set of telephone lines or circuits. The respective nodes are separately coupled to a public switched telephone network, or PSTN,
16
, and are thereby made accessible to their subscribers. Moreover, subscribers of one node can employ messaging to transfer copies of messages (such as voice messages) to subscribers of another node. The respective nodes may or may not share access to each other's voice files (see copending application Ser. No. 09/161,214, filed Sep. 25, 1998, “Multiple Node Messaging System Wherein Nodes Have Shared Access To Message Stores Of Other Nodes”).
An important characteristic of a messaging system is that it be highly reliable and able to quickly recover from system failures. This characteristic is generally referred to as system “availability.” The present invention relates to a messaging system architecture that comprises an NIU and a messaging platform (such as NAP). In such a system, normal processing by the NIU and messaging platform on a given channel can become corrupted due to some failure in either the NIU or the messaging platform. This is commonly referred to as a “protocol violation.” In this situation, the channel on which the protocol violation occurred, or a call on that channel, may become “hung.” The NIU and messaging platform may be unaware that the channel is hung, and may continue to operate as if an existing call is in progress on that channel. However, the telephone network may have long since terminated the actual call on the corresponding voice channel of the telephone network. If a new call comes in from the telephone network on that same channel, it cannot be processed because the corresponding channel in the NIU is hung. The present invention provides a mechanism for preventing such hung calls/channels.
Further background information concerning the construction and operation of messaging systems, and particularly systems employing a Network Applications Platform (NAP) for interfacing a telephone network and network applications running on an enterprise server, may be found in the following patents and copending patent applications, which are hereby incorporated by reference:
U.S. Pat. No. 5,133,004, Jul. 21, 1992, “Digital Computer Platform for Supporting Telephone Network Applications”;
U.S. Pat. No. 5,138,710, Aug. 11, 1992, “Apparatus and Method for Providing Recoverability in Mass Storage Data Base Systems Without Audit Trail Mechanisms”;
U.S. Pat. No. 5,384,829, Jan. 24, 1995, “Digital Computer Platform for Supporting Telephone Network Applications”;
U.S. Pat. No. 5,323,450, Jun. 21, 1994, “Telephone Network Applications Platform for Supporting Facsimile Applications”;
U.S. Pat. No. 5,494,606, Feb. 20, 1996, “Multi-Lingual Prompt Management System for a Network Applications Platform”;
U.S. Pat. No. 5,633,916, May 27, 1997, “Universal Messaging Service Using Single Voice Grade Telephone Line Within a Client/Server Architecture”;
U.S. patent application Ser. No. 08/944,924, filed Oct. 6, 1997, “Enhanced Multi-Lingual Prompt Management in a Voice Messaging System With Support for Speech Recognition”;
U.S. patent application Ser. No. 08/964,744, filed Nov. 5, 1997, “Methods and Apparatus for Providing External Access to Executable Call Flows of a Network Application”;
U.S. patent application Ser. No. 08/987,571, filed Dec. 11, 1997, “Multiple Language Electronic Mail Notification of Received Voice and/or Fax Messages”;
U.S. patent application Ser. No. 09/094,126, filed Jun. 9, 1998, titled “Universal Messaging System Providing Inte

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