Voice mail on the internet

A first Internet telephone system 620 attempts to call with a second Internet telephone system 630 via the Internet 600. However, the second Internet telephone system 630 is not logged onto the Internet at the time of the call. In response to the failed attempt to call, the first Internet telephone system prompts the user to send voice mail to the user of the second Internet telephone system. This results in a phone call over the Internet between a voice mail system 610 and the first Internet telephone system, allowing a greeting to be heard, and a message to be stored. This message may be subsequently retrieved, either using an Internet telephone system over the Internet, or using a standard phone over the conventional telephone network.

TECHNICAL FIELD
 The present invention relates to voice mail systems for use over the
 Internet.
 BACKGROUND OF THE INVENTION
 Conventional voice mail systems (also termed voice messaging systems)
 attach to the telephone network, often via a PBX, and are used to store
 messages from incoming calls when the intended recipient is absent or
 otherwise engaged. The intended recipient can then listen to their stored
 messages at some future time. A voice mail system is generally implemented
 either on special purpose computer hardware, or else on a standard
 computer workstation equipped with a suitable telephony interface. Such
 voice mail systems are well-known; one example is the DirectTalkMail
 system, available from IBM Corporation, which operates in conjunction with
 the DirectTalk/6000 voice processing system (also available from IBM).
 Other examples of voice mail systems are described in U.S. Pat. No.
 5,136,648 and EPA 0588576.
 Also known are electronic mail systems (email), which allow the
 transmission of text messages over a computer network. The most prominent
 such network over the last couple of years is the Internet, which provides
 a readily accessible, worldwide network for packet-based communications.
 Background information about the Internet and the World Wide Web can be
 found in "Spinning the Web" by Andrew Ford (International Thomson
 Publishing, London 1995) and "The World Wide Web Unleashed" by John
 December and Neil Randall (SAMS Publishing, Indianapolis 1994).
 Although originally intended primarily for the transmission of computer
 data, more recently the Internet has been exploited to provide real-time
 telephony communications. The primary attraction of the Internet for
 telephony communications is the charging structure. Thus many Internet
 users have a dial-up connection to an access provider. This is normally
 over a local telephone line, so such users pay only local telephone
 charges when logged on. Some access providers charge a monthly
 description, whilst others charge on the basis of connection time (some
 may do both). However, there is generally no charge associated with actual
 data transfer over the network. As a result, the effective cost of an
 international call over the Internet may be no more than that of a local
 call of the same duration to the access provider. In addition, the fully
 digital nature of the Internet may potentially offer a richer
 functionality (eg in terms of conference calling) than conventional
 telephone networks. Internet telephones are surveyed in the article "Dial
 1-800-Internet" in Byte Magazine, February 1996, p83-88, and in the
 article "Nattering On", in New Scientist, Mar. 2, 1996, p38-40.
 The transmission of voice signals over a packet network is described for
 example in "Using Local Area Networks for Carrying Online Voice" by D
 Cohen, pages 13-21, in "Voice Transmission over an Ethernet Backbone" by P
 Ravasio, R Marcogliese, and R Novarese, pages 39-65, both in "Local
 Computer Networks" (edited by P Ravasio, G Hopkins, and N Naffah; North
 Holland, 1982) and also in GB 2283152. The basic principles of such a
 scheme are that a first terminal or workstation digitally samples a voice
 input signal at a regular rate (eg 8 kHz). A number of samples are then
 assembled into a data packet for transmission over the network to a second
 terminal, which then feeds the samples to a loudspeaker or equivalent
 device for playout, again at a constant 8 kHz rate. Voice transmission
 over the Internet is substantially similar to transmission over a LAN
 (which may indeed provide part of the Internet transmission path), but
 there tends to be less spare bandwidth available on the Internet. As a
 result, Internet telephones normally compress the voice signal at the
 transmitting end, and then decompress it at the receiving end.
 There are several well-known problems with packet-based voice
 communications. Firstly, there is a transmission delay over the network,
 which is variable, depending particularly on the utilisation of the
 network by other nodes at any given time. Thus the arrival of packets at a
 destination node is both delayed and irregular. If the packets were played
 out in irregular fashion, this would have an extremely adverse effect on
 intelligibility of the voice signal. Therefore, packet voice transmissions
 utilise some degree of buffering at the reception end, to absorb such
 irregularities. Such buffering however increases the delay between the
 original voice signal and the audio output at the destination end. This
 delay may cause problems with echos, and more importantly, can render
 natural interactive two-way conversation difficult (in the same way that
 an excessive delay on a transatlantic conventional phone call can be
 highly intrusive). Yet further delays are introduced by the necessity to
 compress/decompress the voice signal.
 Some Internet telephones which are currently commercially available provide
 a voice mail facility, whereby the calling party can leave a message if
 the called party does not answer. This is somewhat analogous to the
 conventional answerphone. Note that such systems are limited in that
 generally the called party is required to be logged onto the Internet to
 receive a voice message. However, many users with dial-up Internet access
 via a modem have to pay on a time basis for a telephone call into their
 Internet access provider, and moreover some Internet access providers
 charge for connections on a time basis. Therefore most users log off from
 the Internet when they are not using it to avoid incurring excessive
 charges. In such circumstances, this implies that they are no longer able
 to receive a voice message.
 It would of course be possible for a user to transmit a voice message in
 the form of a normal email (data) message to another user who is not
 currently logged on. The message is then queued at the Internet access
 provider's site for delivery at next logon by the relevant user. However,
 generally this approach offers few benefits over simply sending an email
 message, rather than the voice message.
 It is an object of the invention to provide improved voice mail facilities
 for the users of Internet telephones.
 SUMMARY OF THE INVENTION
 Accordingly, the invention provides a method of providing voice mail on the
 Internet comprising the steps of:
 selecting to make a call from a first user at a first Internet telephone
 system to a second user at a second Internet telephone system;
 determining that said second Internet telephone system is not currently
 logged onto the Internet to receive said call; and
 transmitting a voice message for said second user over the Internet to a
 voice mail system distinct from said second Internet telephone system for
 subsequent retrieval by said second user.
 The voice mail service is therefore available when the first user cannot
 directly contact the second user. This may be determined as a result of
 actually trying to place a call to the second user, or perhaps simply by
 viewing the list of currently accessible parties. The voice mail system is
 distinct from the second Internet telephone system, and is intended to be
 continuously attached to the Internet. The voice mail system is therefore
 available when the second Internet telephone system is not logged onto the
 Internet, thereby avoiding the subscriber of this second system having to
 pay overly high Internet connection or usage charges.
 In a preferred embodiment, responsive to a determination that the second
 Internet telephone system is not currently logged onto the Internet, the
 first user at the first Internet telephone system is offered a choice of
 whether or not to leave a voice message for the second user. Typically
 this choice is generated locally at the calling Internet telephone,
 although it may be generated at some intermediate server in the network,
 which is used for routing and placing calls. Assuming that the option to
 leave voice mail is accepted, a communications link is established over
 the Internet between the first Internet telephone system and the voice
 mail system in order to transmit the voice message for said second user.
 Said communications link permits two-way communications, and the voice
 mail system transmits to the first user one or more prompts or greetings
 prior to transmission of the message for the second user to the voice mail
 system. Typically, said one or more prompts or greetings include
 information concerning the current location and availability of the second
 user.
 In the preferred embodiment, said voice message can be retrieved by the
 second user either using an Internet telephone over the Internet, or by
 using a conventional telephone over the conventional phone network. It is
 generally most convenient if substantially the same prompts and/or
 greetings are heard irrespective of whether the voice mail system is
 accessed by the conventional telephone network or over the Internet, since
 a subscriber is then only required to keep a single set of
 prompts/greetings up-to-date. Note that one of the advantages of the
 invention is that any voice mail stored in the voice mail system can be
 immediately available for retrieval by the mailbox owner, either by
 calling the voice mail system by telephone, or by Internet access (not
 necessarily via the mailbox owner's normal access provider).
 Preferably the method further comprises the step of the voice mail system
 providing said second user of said second Internet telephone with an
 indication that he or she has a voice mail message waiting next time said
 second user logs on to the Internet using an Internet telephone. This
 indication may be provided in response to a request from the Internet
 telephone, which is transmitted from the Internet telephone to the voice
 mail system at start-up time.
 It is also preferred that this indication is provided irrespective of
 whether said voice mail message was received over the Internet or over the
 conventional telephone network. This emphasises one of the important
 aspects of the invention, namely that a subscriber should only need one
 voice mail service, and the distinction between the Internet and the
 conventional telephone network should be essentially transparent to the
 subscriber.
 The invention also provides a telephone system for making a telephone call
 over the Internet, including:
 means for allowing a first user at said system to select a second user at a
 second Internet telephone system to call;
 means for determining that said second Internet telephone system is not
 currently logged onto the Internet to receive said call; and
 means for transmitting a voice message for said second user over the
 Internet to a voice mail system distinct from said second Internet
 telephone system for subsequent retrieval by said second user.
 The telephone system will typically include means for displaying one or
 more prompts or greetings to said first user in textual or graphical form,
 although usage of this facility may be somewhat restricted in order to
 maintain conformity between the access mechanisms over the Internet and
 over the conventional telephone network.
 The invention further provides a voice mail system including:
 means for receiving a voice message over the Internet;
 means for storing said voice message;
 means for allowing said message to be retrieved over the Internet; and
 means for allowing said message to be retrieved over the conventional
 telephone network.
 In a preferred embodiment, the voice mail system further comprises means
 for transmitting one or more prompts or greetings prior to receipt or
 retrieval of a voice message over the Internet. Generally said one or more
 prompts or greetings transmitted prior to receipt of a voice message over
 the Internet may include information concerning the current location and
 availability of the intended message recipient.
 It is preferred that the voice mail system includes means for receiving a
 voice message over the conventional telephone network, which can then be
 accessed and processed in the same manner as messages received over the
 Internet. Thus a message received over either the Internet or the
 conventional telephone network can be retrieved over either the Internet
 or the conventional telephone network without restriction. Further in this
 vein, preferably there are means for providing an indication to a
 subscriber that he or she has one or more voice mail messages waiting, and
 this indication includes both voice messages received over the Internet,
 and voice messages received over the conventional telephone network.
 In the preferred embodiment, said means for receiving a voice message over
 the Internet includes means for receiving a voice signal in compressed
 form split into a plurality of packets, and means for assembling the voice
 signal and decompressing it into said voice message; and said means for
 allowing a voice message to be retrieved over the Internet includes means
 for compressing the message and packetising it prior to transmission over
 the Internet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 FIG. 1 is a simplified diagram of a voice mail system based on a
 conventional computer workstation comprising system unit 20, display
 screen 12, and keyboard 14. The system unit includes a microprocessor 22,
 ROM/RAM 24, and disk storage 26, connected together via bus 28. In order
 to operate as a voice mail unit, the computer workstation is connected to
 telephone line 66 via a digital trunk processor 64 and a digital trunk
 adapter card 62. The voice mail system also includes a network adapter
 card 30 to connect the voice mail system to a computer network (eg a LAN).
 The voice mail system may also include other known components, such as an
 audio capture/playback card, a CD-ROM and mouse (not shown).
 The voice mail system illustrated in FIG. 1 is based on the DirectTalk/6000
 voice processing system, available from IBM Corporation. The hardware
 components of this system are an RISC System/6000 computer workstation,
 plus the digital trunk processor and digital trunk adapter. The
 DirectTalk/6000 system connects to the telephone network through a T1 or
 E1 digital trunk line 66 (and via a PBX in most installations). The
 digital trunk processor is used to demultiplex incoming signals and
 multiplex outgoing signals on the trunk line, and perform log-linear
 conversion as appropriate. The digital trunk processor is also used to
 perform compression/decompression. The digital trunk adapter effectively
 acts as an interface between the workstation itself and the digital trunk
 processor. Further details about the DirectTalk/6000 voice processing
 system can be found in the manual "IBM AIX DirectTalk/6000, General
 Information and Planning" (publication number GC33-1720-00) and the other
 manuals referenced therein.
 FIG. 2 is a simple block diagram of the main software components running on
 the voice mail system of FIG. 1. Running on the RISC System/6000
 workstation is first of all the operating system for the workstation,
 which in the present case is AIX 110, and then the DirectTalk/6000
 software 120 itself. The latter includes a device driver for the telephony
 hardware (the digital trunk adapter). Also on the RISC System/6000
 workstation, effectively running as an application on top of the
 DirectTalk/6000 system, is DirectTalkMail 130, which provides standard
 voice messaging capabilities.
 It will be appreciated that voice mail systems such as that illustrated in
 FIGS. 1 and 2 are well-known, and that many variations on the system
 illustrated are also well-known. For example, there are many systems in
 which telephone line 66 is analog, in which case the digital trunk
 processor is often omitted, and its functions performed, where appropriate
 by a suitable telephony adapter card. The precise hardware configuration
 employed in the voice mail system is not relevant to an understanding of
 the present invention, and so will not be discussed further.
 The DirectTalkMail voice messaging system itself can be considered as a
 form of voice database system, based on mailboxes. Thus each user or
 subscriber has a mailbox, which has associated with it all the information
 for that user, eg their extension number, their password, the number of
 new messages that they have, their current greeting, and so on. The
 mailbox also logically contains the digitised stored messages for that
 user (although physically the audio recording may be stored in a different
 location from the other information). Each mailbox has a unique
 identifier, such as a number or name, for example, each mailbox can be
 allocated the extension number of the user associated with that mailbox.
 The DirectTalkMail voice messaging system also contains routines to allow
 callers to telephone messages into the database and subscribers to extract
 messages from the database for listening over the telephone, as well as
 other functions such as forwarding messages. The operation of a voice mail
 system in such a manner is well-known and so will not be described
 further.
 FIG. 3 is a simplified schematic diagram of a client computer system which
 may be used for telephone transmission over the Internet. The computer
 workstation of FIG. 3, which is similar to that of FIG. 1, but generally
 less powerful, has a system unit 310 including microprocessor 322,
 semi-conductor memory (ROM/RAM) 324, hard disk 326, and a bus over which
 data is transferred 328. Other typical components of the computer are a
 display 312, keyboard 314, and mouse (not shown). The computer of FIG. 3
 may be any conventional workstation, such as an Aptiva computer, available
 from IBM Corporation. Alternatively, any other form of suitable Internet
 access device, including the new generation of low-cost systems
 (effectively sub-PCs) which are currently being developed may be employed
 instead as the client telephone terminal.
 The computer of FIG. 3 is equipped with two adapter cards. The first of
 these is a network adapter card 330. This card, together with accompanying
 software such as the TCP/IP communications stack, allows messages to be
 transmitted onto and received from a computer network such as a Local Area
 Network (LAN). In this case, it is presumed that the Internet is accessed
 via the LAN. Alternatively (or additionally), the computer of FIG. 3 may
 have a modem (not shown), installed either internally as another adapter
 card, or externally, for example via the RS-232 serial port. The modem in
 turn can be connected to a telephone socket, allowing dial-up access to an
 Internet provider. The operation of a network adapter card or modem to
 provide Internet access is wellknown, and so again will not be described
 in detail.
 The second card shown in FIG. 3 is an audio card 362 which is connected to
 a headset including microphone 366 and earphones 364 for audio input and
 output respectively (alternatively the computer in FIG. 3 may have a
 loudspeaker, and built-in microphone, but the use of a headset is
 preferred to optimise the quality of the audio signal produced and
 actually heard).
 The audio card is shown in more detail in FIG. 4. The card illustrated and
 used in the preferred embodiment is an M-Wave card available from IBM
 Corporation, although other cards are commercially available that perform
 an analogous function. The card 362 contains an A/D converter 442 to
 digitise incoming audio signals from the attached microphone 366. The A/D
 converter is attached to a codec 444, which samples the incoming audio
 signal into samples (eg 8 bit or 16 bit). Digitised samples are then
 passed to a digital signal processor (DSP) 446 on the card via a buffer
 448 where they are compressed. The DSP is controlled by one or more
 programs stored in semiconductor memory 452 on the card. Data can be
 transferred by the DSP to and from the main PC bus.
 Audio signals to be played out are received by the DSP 446 from the PC bus
 328, and processed in a converse fashion to incoming audio. That is, the
 output audio signals are passed through the DSP 446 for decompression, and
 then through buffer 450 to the codec 444, from there to a D/A converter
 454, and finally to a loudspeaker 364 or other appropriate output device.
 There are various compression/decompression techniques that are available
 for audio communication over the Internet. The preferred embodiment uses a
 modified version of GSM, which is the standard compression technique used
 in Europe for cellular phones, to provide voice compression. Another
 possible technique to use is the DigiTalk system developed by Rockwell
 Communications. Such technologies as these reduce the bandwidth
 requirements for voice communications to less than 10 kbits per second.
 Note that although the embodiment shown in FIG. 4 performs the
 compression/decompression on a DSP, in other embodiments this processing
 may be performed purely in software on the host computer.
 In order to operate as an Internet telephone, the computer system of FIG. 3
 must contain appropriate application software. In the preferred
 embodiment, this application software is called WebTalker, and provides a
 user interface as shown in FIG. 5. This interface includes message panel
 505, which can be used to pass status messages to the user (eg "dialling",
 "engaged", etc), and a set of control buttons 510. The Call button 511
 allows a call to be made to a named individual, whilst the User List
 button 512 provides access to a server directory (see below), as well as
 to a listing of people who have been called previously (or from whom calls
 have been received). Clicking on the name of a desired individual from one
 of these lists results in a call being made to the corresponding email
 address for that individual. The remaining control buttons, Set-Up 513,
 Help 515, Mute 514 and Exit 516 are substantially self-explanatory, and
 will not be described further since they are not directly relevant to an
 understanding of the present invention.
 The window also contains slider bars, which can be used to control Volume
 530, Voice Quality 531, and Microphone Sensitivity 532. It will be
 appreciated that it is possible to improve voice quality for example by
 reducing the degree of compression, or by increasing the amount of
 buffering at the receiving end, although these will tend to lead to
 increased delays. Finally, the window contains Mail Waiting light 520 and
 Voice Mail light 525, which will be explained in more detail below.
 The operation of the Webtalker telephone is as follows (see FIG. 6). When
 the user starts up the Webtalker software telephone client 620 on the
 Internet 600, the telephone logs onto a server 650 on the Internet. There
 may be multiple possible servers, but a default one is chosen in
 accordance with the set-up parameters of the Internet telephone. It will
 be appreciated that this requires the Web telephone to use standard
 Internet communications facilities, as wellknown in the art.
 The server maintains a list of people currently logged on to the Internet
 and using Webtalker. This list is accessible to the user (via the User
 List control button), allowing the user to select another party to call.
 The called party then receives notification of their incoming call in
 their control window 505, plus a pop-up box asking them whether or not
 they wish to accept the call. Assuming the call is accepted, then this
 establishes a direct link between the two clients (ie the two Internet
 telephones) independent of the server. This link provides a TCP/IP control
 channel and a UDP data channel. The two clients can start audio
 communications, using their audio subsystems as described above. Thus the
 audio data from each client is processed into a compressed form, and then
 transmitted over the UDP data channel to the other client. The audio
 communications can either be full duplex, or, to save bandwidth, half
 duplex.
 In practice although the audio quality across the network is acceptable,
 the end to end delay Internet may be a couple of seconds or more, which
 means that completely natural conversation is not possible. Thus it can
 become confusing if one party tries to interrupt another, or does not
 clearly indicate when he or she finishes speaking. However, once a user is
 accustomed to these limitations, then an Internet telephone conversation
 becomes a very valuable method of communication.
 As so far described, the WebTalker application has substantially the same
 function as known Internet telephones, and so its operation will be well
 understood by the skilled person. However, in accordance with the present
 invention, the WebTalker telephone includes the additional facility of
 allowing a voice message to be left when the called party is not logged
 onto the Internet. This is to be contrasted with the situation with known
 Internet telephones, which at the called end provide a voice mail message
 when the called party is logged onto the network, but chooses not to
 answer an incoming call. As explained previously, most users, particularly
 those at home, do log-off from the Internet when not specifically using it
 to avoid paying unnecessary connection charges.
 There can be several reasons why a call might be made to a party who is not
 currently logged on. One possibility is for the server list to be in
 error, perhaps because of a recent failure in the network, which has not
 yet been reflected in the list. Another possibility is that a caller
 exited abnormally from the Webtalker application (eg they crashed out),
 and so did not trigger the normal log off procedure at shut-down (normally
 the server would eventually time out with respect to these terminals, and
 eventually log them off anyway). Another possibility is that the call is
 made using the Call button 511, with the address of the called party
 directly entered, therefore by-passing the server list of users currently
 logged on (not all Internet telephones enable this).
 FIG. 6 illustrates the situation where client 1 has a first WebTalker
 telephone 620, connected to the Internet 600 typically via a modem and
 telephone line 625. Likewise client 2 has a WebTalker telephone 630, and a
 similar dial-up connection 635 to the Internet. However, client 2 is not
 currently logged onto the Internet, so this connection is shown in a
 dashed line.
 At this point, when client 1 tries unsuccessfully to make a call to client
 2, the WebTalker telephone of client 1 provides a status message
 indicating that the call could not be made because client 2 is not
 currently logged onto the network. Further, the WebTalker telephone
 invites client 1 to leave a voice mail message for client 2. Assuming that
 client 1 does opt to leave a voice mail message, then the WebTalker
 telephone dials up the voice mail system 610 in exactly the same manner as
 dialling any other WebTalker telephone on the Internet.
 In the preferred embodiment, the option of sending voice mail is therefore
 controlled by the calling Internet telephone without reference to the
 server. However, as an alternative, the server may be involved. For
 example, in addition to presenting a list of users currently logged on,
 the server may present an additional list of callers for whom voice
 messages can be left. Selecting a caller from this list results in a call
 being made to the voice mail system, in the same manner that selecting a
 currently logged on user results in a call to that user. In such
 circumstances, it may in fact be desirable for the voice mail system
 itself to log onto the server.
 In general, the voice mail system 610 will have the capability to handle
 many lines of incoming traffic, and have a permanent connection into the
 Internet. The voice mail system 610 will typically be managed by a service
 provider. Client 2 may pay a subscription for this service, or it might
 perhaps be included free with an Internet access package, or telephone
 line rental, in order to encourage usage. Similarly, an organisation
 marketing Internet telephones might offer the voice mail service to
 attract users to their particular offering. Alternatively, a company might
 provide the voice mail system 610 for all its employees.
 It is assumed that client 1 was informed of the Internet address of the
 voice mail system 610 for client 2 at the same time that it learned of the
 Internet address of client 2, and that these have been stored together in
 a directory on client 1. It may also be possible for client 1 to
 interrogate the server 650 to find out the address of the voice mail
 system for client 2; or as suggested above, the connection may in fact be
 initiated through the server. Alternatively it may be that all subscribers
 to the WebTalker Internet telephone may use the same voice mail service.
 However, in the event that the WebTalker telephone is unable to determine
 the address of the voice mail system for client 2, then an appropriate
 error message is supplied to client 1.
 FIG. 7 illustrates the enhancements necessary to the voice mail system 610
 in order to allow it to receive calls from the WebTalker telephone. As
 shown previously in FIG. 2, the DirectTalkMail system 730 is essentially
 an application running on top of the DirectTalk/6000 voice processing
 system 720, which itself is an application running on top of the AIX
 operating system 710 to provide recording and playout of voice segments
 etc. Included within the DirectTalk voice processing system is a custom
 server interface 725, which allows C programs to interact directly with
 the DirectTalk/6000 voice database. Use of the custom server interface is
 required in the present instance since the voice messages are not being
 played out over the standard telephone interface (via the digital trunk
 adapter), but rather transmitted in software format over the Internet. The
 custom server interface is described in more detail in the manual IBM AIX
 DirectTalk/6000 Voice Application Development (reference SC33-1722-00).
 In order for the DirectTalkMail to receive WebTalker telephone calls,
 appropriate software has to be provided. This software can effectively be
 split into two components, with an interface between them. The first
 component provides the WebTalker interface 750, and includes
 communications software 760 to allow communications over the Internet (nb
 some of the software necessary for this is already provided in the
 operating system 710, as known in the art). The WebTalker interface
 software 750 ensures that to a client WebTalker telephone, such as
 WebTalker telephone 620 (see FIG. 6), the voice mail system can appear
 substantially similar to another WebTalker telephone. Therefore, when the
 voice mail system needs to play out a prompt over the Internet, the
 WebTalker IF component 750 is responsible for compressing the audio,
 packaging it correctly, and transmitting it out over the Internet to the
 client system. Conversely, for incoming audio from the client system, the
 WebTalker IF component is responsible for decompressing, buffering, and
 assembling the received packets into a proper audio signal. Note that this
 processing may be done all in software (ie there is no need for special
 hardware at the voice processing system such as that shown in FIG. 4).
 The DirectTalkMail interface component 740 is therefore passed incoming
 audio signals in PCM format from the WebTalker interface (A law, mu law,
 or any other suitable digital audio format could be used), and uses the
 DirectTalk/6000 custom server interface to store these as voice messages
 in the DirectTalk/6000 voice database. Similarly, the DirectTalkMail
 interface component uses the custom server interface to retrieve stored
 prompts and voice messages, converts to the appropriate format (eg PCM)
 and passes these over to the WebTalker interface component for
 compression, and transmission to the client. Each mailbox in the voice
 database may have an assigned Internet address, so that calls intended for
 a client at a particular Internet address (as specified by the information
 received from the WebTalker interface component) can be stored in the
 correct mailbox (alternatively incoming calls could be required to specify
 a mailbox number). It will be appreciated that in common with most voice
 mail systems, DirectTalkMail actually performs its own compression on
 voice messages prior to storage, to reduce storage requirements. The
 compression technique used by the voice mail system differs from that used
 by the WebTalker telephone system, hence the need to decompress and the
 recompress incoming calls (and similarly for outgoing calls), although it
 is certainly feasible for a voice mail system and Internet telephone to
 use the same compression scheme throughout.
 The most basic embodiment of the present invention simply allows for the
 two-way transmission of audio, enabling the caller to hear a greeting or
 prompt, and then to leave a message. However, it will be appreciated that
 the DirectTalkmail system, in common with most voice mail systems, is
 normally controlled by a user pressing DTMF keys on their telephone to
 select between multiple commands or options. In order to provide this
 control to a client over an Internet, a facility is added to the WebTalker
 telephone, such that when it dials a voice mail system, a telephone keypad
 is presented to the user of the WebTalker telephone. By clicking on the
 desired button (ie digits 0-9, * or #), the user of the WebTalker
 telephone can transmit a control command to the voice mail system. The
 selected command is not transmitted as a DTMF signal, but rather as a
 simple message containing an identifier of the pressed key, since this
 requires far less bandwidth. This identifier is distinguished from normal
 audio data, so that it is properly recognised by the WebTalker interface
 component 650. The identifier is then passed to the DirectTalkMail
 interface, which interacts with the DirectMail and DirectTalk/6000 systems
 to ensure that the requested function is performed.
 The two-way audio exchange between the voice mail system and the client
 Webtalker telephone, together with the facility for the client to send and
 the voice mail system to accept identifiers corresponding to DTMF tones,
 provide a full function voice mail service, thereby allowing (for example)
 client 1 to leave a voice mail message for client 2, when client 2 is not
 logged onto the Internet to personally receive a telephone call. It will
 be appreciated that voice mail system 610 can typically accept many
 incoming calls simultaneously. Indeed, unlike conventional operation of a
 voice mail system, which is limited by a predetermined number of telephone
 ports, there is not necessarily any hard limit on the number of software
 Internet calls which can be handled at the same time (rather, as the
 number of calls increase, performance will eventually start to degrade,
 due to the finite processing power available at the voice mail system, or
 the limited bandwidth of the voice mail Internet connection, or both).
 Once a voice mail message has been stored within the voice mail system 610,
 then there are several possible mechanisms for retrieving it. Firstly, the
 message can be retrieved in conventional fashion over the normal telephone
 network. Thus the user simply dials the telephone number associated with
 the voice mail system, and can then access any messages they have by
 responding to appropriate prompts, and (generally) entering a password.
 Another possibility is that the message can be retrieved over the Internet
 using a Web browser with audio capability. This can be implemented by
 having the voice mail system act as a WWW site, with universal resource
 locators pointing to a user mailbox, and the mail messages within. This
 approach is described in more detail in PCT application PCT/GB95/02009,
 and is also provided by the currently available release of the
 DirectTalk/6000 and DirectTalkMail products (see the manual IBM AIX
 DirectTalkMail Administration, reference SC33-1733-00). As a slight
 variation on the approach described therein, once a message has been
 selected, the Web browser may also provide the option of having this
 message delivered to the user's Internet telephone system (which will
 generally be running on the same machine as the browser). It may be
 advantageous to have the Internet telephone system play the message
 (rather than the browser itself), for example because the former allows
 the message to be subsequently forwarded, or will allow the caller's
 address to be stored in the user's directory.
 The preferred embodiment provides another possibility, that of accessing
 the stored voice mail message from a WebTalker telephone. Thus as part of
 its start-up procedure, the WebTalker telephone interrogates the voice
 mail system associated with that client (this can be specified as part of
 the set-up procedure). The Webtalker telephone client therefore sends a
 query to the voice mail system, which is received by the WebTalker
 interface component and passed into the DirectTalkMail system. The
 DirectTalkMail system then identifies the mailbox corresponding to the
 specified Internet address for that client, and returns an indication of
 whether or not there are any new messages for that user. This indication
 is returned by the WebTalker interface component to the requesting
 WebTalker telephone, and if positive, the message waiting indicator on the
 WebTalker telephone client screen is activated (eg by highlighting or
 making a different colour).
 In order to access the voice messages, the client Internet telephone then
 places a call over the Internet to the voice mail system. This is done by
 simply pressing the voice mail button, which automatically dials the
 default voice mail system for that client. This establishes a two-way
 audio call between the client Internet telephone and the voice mail
 system. The call can now proceed in analogous fashion to that described
 above for entering a voice message into the system. Again, the voice mail
 system plays various prompts to the user, who is provided with a simulated
 DTMF keypad on his or her screen. The user selects the desired button, and
 can navigate through the voice mail system, including typically some
 password protection, to obtain access to their voice mail, which can then
 be played out to them over the Internet. Thus the user can have immediate
 access to their voice mail, either via the conventional telephone network,
 or from any location on the Internet.
 It will be appreciated that many variations on the above approach are
 possible. For example, instead of using a simulated DTMF keypad for
 inputting control commands, it may be possible to include a voice
 recognition facility with the voice mail system to allow a client to
 simply speak his or her desired choice. Another possibility is for all
 prompts from the voice mail system to be available for transmission in
 text form to a client, and displayed there textually or graphically, eg
 perhaps using a menu structure, thereby significantly reducing bandwidth
 requirements and overall delay. It is also possible for DirectTalkMail to
 exploit the enhanced user interface of the client (compared to a
 conventional telephone) to provide information in a more convenient format
 to the client. For example, rather than asking a user to "Press 1 to hear
 messages" (say), the system might simply display the command "Listen to
 messages", with associated button. Selecting this button would then result
 in the voice mail system taking the same action as if a "1" had been
 pressed on a conventional telephone. The enhanced capabilities of the
 screen interface may be further exploited to provide the user with
 features that are not directly available when calling from a conventional
 telephone. For example, the voice mail system could send a text list of
 stored messages, together with information such as the sender of the
 message, to allow a user to immediately assess all his or her outstanding
 messages (nb this is the approach taken with the voice mail Web browser
 access described above).
 It will be appreciated that although the systems described so far transmit
 telephone calls entirely over the Internet, for some Internet telephone
 systems it is in fact possible to make hybrid telephone calls. In these
 cases the originating or destination telephone may in fact be a
 conventional telephone, with one or more servers acting as interface units
 between the Internet and the conventional telephone network (indeed, the
 voice mail system itself may possibly be so connected). As used herein,
 the term "Internet telephone" is generally meant to cover such systems,
 and references to transmission over the Internet may include transmission
 over the conventional telephone network along some of the route.
 It is possible for the voice mail service described above to be invoked not
 only when the called party is not logged onto the Internet, but even when
 they are logged on, but unable or unwilling to accept the call at the time
 that it is received. This would avoid the need for an Internet telephone
 to provide a local voice mail service. In this case, the Internet
 telephone, in refusing to accept a call, could transmit back to the
 calling party the Internet address of its preferred voice mail system.
 There are also many possibilities for the action to be taken by the voice
 mail system on receipt of an incoming voice message. For example, it might
 try to page the intended recipient, or possibly place a telephone call
 through to them at a previously indicated location. Another possibility is
 to send an email notification to them, to be read next time they log on to
 the Internet.
 It will be recognised that one of the drawbacks with current Internet
 telephones is that systems from different vendors are generally
 incompatible with one another. Although efforts are being made to provide
 standardisation, it will be noted that the voice mail system of the
 present invention may easily be adapted to support multiple formats. The
 simplest way of achieving this is to have software which is the equivalent
 of the WebTalker interface 750 and communications layer 760 for each
 different telephone format, with incoming/outgoing calls being identified
 and passed to the correct interface software.
 An important aspect of the invention is that allows a subscriber to
 maintain a single voice mailbox, accessible either over the Internet, or
 the conventional telephone network. Thus a user has only a single greeting
 response to maintain (eg to inform callers if the user is eg in a meeting,
 away on vacation, or whatever). Furthermore, voice mail messages may be
 treated in exactly the same manner, whether received over the Internet or
 conventional telephone network, and whether accessed and retrieved via the
 Internet or the conventional telephone network. For example, when a user
 may notified of the number or existence of new or stored messages, without
 any distinction as to the origin receipt mechanism of the messages. The
 voice mail system of the invention therefore offers the user greater power
 and flexibility, without any corresponding increase in complexity.