Patent Publication Number: US-8542807-B2

Title: Method and apparatus for establishing a data link based on a pots connection

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to video and/or audio conferencing over a digital network. More particularly, the invention provides a way to set up a video and/or audio conference automatically by leveraging machine-readable features or content from a previously established dial up telephone call. 
     2. Description of the Related Art 
     The increasing ubiquity of digital network access has led to a corresponding increase in the number of digital communications applications available to the consumer. The capabilities offered by voice-over-internet-protocol (VoIP) systems, video teleconferencing software, and other distance collaboration tools far exceed those available over traditional voice phone lines. Nonetheless, many users still find such applications inconvenient to use. User frustration stems from the relative complexity of installation and configuration, poor reliability, variable connection quality, incompatibility among competing systems, and the increased effort required to establish connections during subsequent use. 
     For instance, with a video conference call under today&#39;s technology, the participants must operate their computers to obtain an IP address, note this IP address, and then send the IP address to the other participants by email, chat, or phone. Each participant must also wait to receive the others&#39; IP addresses by email or chat or phone, make a note of them, and enter the received IP addresses in their own video conferencing software. Finally, with all data entered, the participants wait for their video conferencing software packages to interconnect. For many users, this is a time-consuming, frustrating process, fraught with technical minutiae. 
     While many applications do simplify the connection process by saving the settings for frequently established connections as “sessions,” none have matched the convenience, universality, and reliability offered by Plain Old Telephone Service (POTS). 
     SUMMARY OF THE INVENTION 
     After parties form a dial up voice telephone connection, the parties&#39; respective communications devices automatically create or leverage machine readable features or content of the telephone connection to identify the parties to each other or to a rendezvous server, and thereafter the communications devices and/or the rendezvous server automatically establishes a data link between the parties. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows an overall system view, in block diagram. 
         FIGS. 1B-1C  show some different communications devices, in block diagram. 
         FIG. 2  is a block diagram of a digital data processing machine. 
         FIG. 3  shows an exemplary storage medium. 
         FIG. 4  is a perspective view of exemplary logic circuitry. 
         FIG. 5  is a flowchart of a method for establishing a data link. 
     
    
    
     DETAILED DESCRIPTION 
     One aspect of the invention is a communications device that leverages machine-readable content or features of a POTS connection to establish a data link over a digital network automatically. Establishing the data link requires little or no effort from the user beyond that required for establishing the POTS connection, i.e., dialing a phone number). This device is fully functional as a conventional POTS phone. For instance, the device may have the look and feel of a traditional phone, and allow a user to establish a POTS connection through the familiar dialing process. The device may also offer handset, headset, and speakerphone functionality. 
     Additionally, the device is capable of communicating over a digital network, and may include additional input/output devices, e.g., a still or video camera, keypad, keyboard, color display, or video input/output ports, for receiving and rendering information transmitted and received over the data link. Thus, the device is capable of establishing a digital communications link, as well as a POTS connection with one or more remote devices, as well as one or more conventional POTS telephones. Once established, the data link is used to transfer data that enhances the interaction provided by the POTS connection. 
     Hardware Components and Interconnections 
     Overview 
     System Architecture 
       FIG. 1A  shows a system  100  for establishing a data link between two or more parties. In addition to “data link,” this disclosure may also employ other terms such as digital connection, data connection, digital call, and the like, without any intended limitation. 
     Parties to this data link are indicated by  106 ,  108 . Optionally, one or more third parties party such as  104  may also participate, but this example uses two parties to illustrate the concepts. Each party has a novel communications device  107 ,  109  (hereinafter “device”), which includes a telephone and a computer, as discussed in detail below. The telephone is electrically connected to the computer or integrated into the computer. First, the parties  106 ,  108  establish a normal, dial-up telephone call via the POTS network  111 , either directly or through a conference calling bridge  115 . The devices  107 ,  109  link to the POTS network  111  via links  120 ,  122 . 
     As explained in greater detail below, the devices  107 ,  109  leverage this POTS call to establish a data link automatically over the digital network  112 , with a minimum of effort by the human parties. In one embodiment, the devices  107 ,  109  exchange network addresses using acoustic signals conveyed over the POTS network  110 , and then use these network addresses to set up a data link over the digital network  112 . In another embodiment, the devices  107 ,  109  employ a rendezvous server  114 , and devices  107 ,  109  or the bridge  115  uses caller ID or another calling number identification (CNID) code to identify the devices to the rendezvous server  114 . The server  114  uses the identifying information to match the participating devices, and then completes, or instructs the parties to complete, the data link. In a different embodiment, the devices  107 ,  109  compute a digital soundprint based on content of the POTS call, and submit their soundprints to the server  114 . The server, encountering matching soundprints, completes or instructs the parties to complete the data link. Without any intended limitation, the term “soundprint” is used for ease of explanation, but this feature may also be referred to as an “acoustic fingerprint” or “digital fingerprint.” 
     As mentioned above, the system  100  may optionally employ a conference calling bridge  115  to aid in setting up the POTS connection between the parties  106 ,  108  (and  104  if applicable). In one embodiment, the bridge  115  is implemented by systems providing conventional POTS conference calling, such as those provided by companies such as AT&amp;T, Sprint, MCI, and the like. In a different embodiment, the bridge  115  may be implemented by proprietary equipment operated by entity that operates the rendezvous server  114 , or an affiliate of this entity, in which case the bridge  115  and server  114  equipment may be (optionally) combined. 
     POTS Network. 
     This disclosure uses the term “POTS” for brevity, ease of description, and accuracy as to most embodiments. This term is used as a convenient handle for any publicly accessible telephone network that people can conveniently access by dialing a telephone number. The network may be partially or completely public. One example is a network of mostly copper lines and microwave relays, known as the public switched telephone network (PSTN). However, the POTS network  110  also contemplates the use of satellite phones with one or both parties  106 ,  108 . Furthermore, as VoIP communications become more popular, there may come a day when people commonly dial telephone numbers using VoIP telephones, pay telephones utilize VoIP technology, and peoples&#39; homes use VoIP telephones primarily. The POTS network  110  includes all of these, and any conceivable alternatives for humans to conveniently place a telephone call to another party by dialing a number. 
     Digital Network. 
     The network  112  may be implemented in various forms of packet switched digital communications network. One example is the public Internet. Other examples include a private Intranet, wide area network, local network, or any other network providing sufficient functionality for the purposes described herein. Devices on the network  112  have a unique address, such as an IP address in embodiments that use Internet Protocol. 
     Rendezvous Server. 
     The server  114 , coupled to the network  112 , may be implemented by any computing device of suitable processing and storage ability to fulfill the functional requirements discussed herein. Broadly, the server  114  acts as a rendezvous site to receive and verify data link setup requests from the parties and, once verified, to advise each party of the other party&#39;s network address or to form a connection between the parties. The server is well known to all parties equipped with a communication device (such as  107 ,  109 ). The devices  107 ,  109 , for example, may have the server&#39;s addresses or other unique identification embedded in the devices&#39; storage. The server may also be implemented by a distributed network of computers sharing the duties of facilitating call connection using well known addresses or network port numbers. 
     Communication Devices 
       FIGS. 1B-1C  show two different embodiments of a communication device. In each of these examples, the illustrated communication device includes a telephone component and a computer component, as explained below in greater detail. In both examples, the telephone component is electrically connected or integrated into the computer. The telephone component is used to place a POTS telephone call. The computer component assists with a process of leveraging the POTS call or a machine-readable feature of the call to identify the parties and automatically establish a data link between confirmed parties. 
     The arrangement  150  ( FIG. 1B ) uses a telephone that is integrated into the computer, and may even be indistinguishable from the computer. This approach avoids having to use a conventional telephone. In contrast, the arrangement  170  ( FIG. 1C ) uses a conventional telephone  175 , along with various computer components. 
     Referring to  FIG. 1B , a user interface  158  includes a microphone and speaker, as well as a physical keypad, touch screen video keypad, or any one of the many well-known human interfaces for dialing. The interface  158  also includes a display for use in video conferencing, which may be satisfied by a video monitor of any technology suitable to the purposes described herein. Also included in the interface  158  is some video capture means such as a webcam, still camera, video camera, etc. This is used to convey the party&#39;s image to other parties of the data link. These various components of the user interface  158  are described together, as they all satisfy a user interface function, and they can (but need not) be integrated in hardware. 
     In the embodiment of  FIG. 1B , the user dials a telephone number using the user interface  158 . The CPU  156  operates the POTS interface  152  to place the POTS call. The interface  152  may be satisfied by a telephone DAA (direct access arrangement) for example, or another known component capable of satisfying the functional requirements of this disclosure. Ultimately, the CPU  156  employs the digital interface  154  to connect to the other party via the digital network  112  ( FIG. 1A ). The interface  154  may be implemented by a broadband modem, Ethernet card, wireless modem, or satellite interface, to name a few options. The device  150  also includes digital data storage  157  coupled to the CPU  156 , for long-term storage of data such as the associated party&#39;s telephone number, a network address or domain or URL of the rendezvous server  114 , and other such data. 
     Turning to  FIG. 1C , the arrangement  170  includes some computer components along with a conventional telephone  175 . In the case of a landline home telephone, the telephone  175  would normally be attached to an RJ-11 jack  171  or other wall socket via a cord  174 . However, in this embodiment, the cord  174  is removed, and the CPU  180  (and some interfaces  178 - 179 ) are inserted between the telephone  175  and the jack  171 . 
     The phone interface  179  is implemented by hardware such as a DAA (direct access arrangement), Analog-to-Digital Converters, Digital-to-Analog Converters, Audio Codecs, amplifiers, etc. The components  178 ,  176 ,  180 , and  181  may be implemented as described for similarly named components ( 152 ,  154 ,  156 ,  157 ) from  FIG. 1B . 
     In the example of  FIG. 1C , since dialing is accomplished on the telephone  175 , then the user interface  177  need not include a keypad, and in fact, a single pushbutton, flip switch, or other input tool may serve well to start and stop the digital link. On the other hand, the CPU  180  may complete and/or conclude the digital link automatically, in which case the single key button may be omitted as appropriate. The interface  177  nevertheless includes the same microphone, speaker, camera, and video monitor components as with the interface  158  of  FIG. 1A . 
     Data Processing Components 
       FIGS. 1A-1C  depict various data processing components. These may be implemented by hardware, software, firmware, or a combination of these. The makeup of these subcomponents is described detail below with reference to  FIGS. 2-4 . 
     Digital Data Processing Apparatus 
     One example for implementing data processing components is a general purpose processor, microprocessor, controller, microcontroller, state machine, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, personal computer, mainframe computer, computer workstation, or any combination designed to function as described herein. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     As a more specific example,  FIG. 2  shows a digital data processing apparatus  200  with a processor  202  coupled to a digital data storage  204 . Here, the storage  204  includes a fast-access storage  206  and nonvolatile storage  208 . The fast-access storage  206  may be used, for example, to store the programming instructions executed by the processor  202 . The storage  206  and  208  may be implemented by various devices, such as those discussed in greater detail in conjunction with  FIGS. 3 and 4 . 
     The apparatus  200  also includes an input/output  210 , such as a connector, line, bus, cable, buffer, electromagnetic link, network, modem, transducer, IR port, antenna, or other means for the processor  202  to exchange data with other hardware external to the apparatus  200 . 
     Storage Media 
     As mentioned above, some of the disclosed components employ digital data storage. Depending upon its application, this digital data storage may be used for various functions, such as storing data, storing machine-readable instructions, or both. These instructions may carry out the ultimate processing functions, or they may serve to install a software program upon a computer, where such software program is then executable to perform the ultimate processing functions. 
     In any case, the storage media may be implemented by nearly any mechanism to digitally store machine-readable signals. One example is optical storage such as CD-ROM, WORM, DVD, digital optical tape, disk storage  200  ( FIG. 2 ), or other optical storage. Another example is direct access storage, such as a conventional “hard drive”, redundant array of inexpensive disks (“RAID”), or another direct access storage device (“DASD”). Another example is serial-access storage such as magnetic or optical tape. Still other examples of digital data storage include electronic memory such as ROM, EPROM, flash PROM, EEPROM, memory registers, battery backed-up RAM, etc. 
     Logic Circuitry 
     In contrast to storage media that contain machine-executable instructions (as described above), a different embodiment uses logic circuitry to implement processing functionality. Depending upon the particular requirements of the application in the areas of speed, expense, tooling costs, and the like, this logic may be implemented by constructing an application-specific integrated circuit (ASIC) having thousands of tiny integrated transistors. Such an ASIC may be implemented with CMOS, TTL, VLSI, or another suitable construction. Other alternatives include a digital signal processing chip (DSP), discrete circuitry (such as resistors, capacitors, diodes, inductors, and transistors), field programmable gate array (FPGA), programmable logic array (PLA), programmable logic device (PLD), and the like.  FIG. 4  shows an example of logic circuitry in the form of an integrated circuit  400 . 
     Operation 
     Introduction 
     Having described various structural features, some operational aspects are described next. Referring to  FIG. 5 , the sequence  500  first establishes a POTS connection ( 502 ). Then, the sequence  500  leverages machine-readable content or features of the POTS connection to establish ( 506 ) a data link between the parties. 
     This data link is used to conduct a video, including still and/or motion video, and/or audio conference between the parties using packet switched digital data over the digital network  112 . The POTS connection may be kept or disconnected ( 510 ). If the POTS connection is kept, the POTS connection may be maintained to provide audio, in which case the data link may be used exclusively for video, presentations, multimedia, and the like. If the POTS connection is disconnected, the data link also transmits the audio portion of the connection. Further operations ( 512 ) may be performed during the video conference, as discussed in detail below. The data link is ultimately disconnected in step  514 . The POTS connection, if retained in step  510 , is disconnected in step  516 , which may occur concurrently with disconnection ( 514 ) of the data link, or before, or after. 
     Without any intended limitation, details of the sequence  500  are discussed primarily using the example where the party  106  (calling party) initiates a POTS call to the party  108  (called party) in accordance with  FIG. 1A , where each party uses a device  170  as shown in  FIG. 1C . 
     POTS Call Setup 
     In step  502 , the calling party  106  uses the telephone  175  to dial the party  108 . The call rings through, the party  108  answers, and the POTS connection is established via  120 ,  111 ,  122 . Alternatively, each of the parties  106 ,  108  uses its respective telephone ( 175 ) to dial the bridge  115 , which connects the POTS call. In the case of three or more parties, each party calls the bridge  115  in this manner. 
     Setup of Data Link 
     Introduction 
     In step  506 , one or all of the parties  106 ,  108  initiate the data link, or this may occur automatically in response to one or more parties&#39; CPUs  180  sensing a completed POTS call. In one example, a party can initiate the data link via the user interface  177 , for example by pushing a “DATA CONNECT” or “IDENTIFY” button, or entering a prescribed keypad sequence, or uttering a prescribed voice command, etc. 
     In step  506 , the parties&#39; respective devices  107 ,  109 , and optionally the rendezvous server  114 , advantageously leverage machine-readable content or features of the POTS connection to automatically establish the data link, while requiring minimal user input. As described in detail below, step  506  may be carried out in different ways ( 506   a - 506   c ). These may be different alternatives of implementation, or all of these approaches may be implemented concurrently and available to parties in order to offer users a greater number of call setup options. 
     Acoustic Signals  506   a  (No Rendezvous Server) 
     For ease of discussion, the example of  506   a  is first described in the context of two parties. Here, the initiating party  106 &#39;s CPU  180  transmits machine-readable acoustic signals to the other party via the POTS interface  178 , line  172 , jack  171 , link  120 , network  111 , and link  122 . The receiving party  108  sends and receives similar signals in like fashion, back to the party  106 . These exchanged signals contain the minimum information needed to setup a data link via the network  112 , including at least the parties&#39; respective addresses on the digital network  112 . If the parties&#39; devices  170  are not already connected to the network, the devices CPUs  180  direct their respective interfaces  176  to connect to the network  112  and obtain a network address. The network address may be, for example, an IP address. Thus, in step  506   a , both parties  106 ,  108  work together via the POTS call to discover each other&#39;s presence on the network  112 . 
     Optionally, the devices  170  may take steps to minimize the acoustic signal&#39;s disruption to voice communications on the POTS call. For example, the devices  170  may limit the acoustic signals exchanged over the POTS call to short duration bursts, or conduct them over a long time using a low volume. Furthermore, information communicated by the devices over the POTS connection may be compressed as fully as possible prior to transmission. 
     The devices may transmit the acoustic information using conventional acoustic encoding schemes, such as DTMF or text-to-speech and voice-recognition. Alternatively, the devices may encode the information within less intrusive audio that can be decoded by the receiving devices. For example, a party&#39;s device may steganographically encode the information within a synthesized voice announcing the identity of the party, or modulate the clicks and pops commonly observed within the existing noise floor. In a further embodiment, the devices may transmit the information in a manner completely inaudible to the users, e.g., using frequency division multiplexing. 
     If the digital network  112  is a routed network, e.g., the network address is an IP address, each party&#39;s receipt of the other&#39;s network address effectively establishes a data link, in that each party&#39;s device is now reachable by the other party&#39;s device. If the digital network supports persistent, dedicated data links between devices, each of the devices receiving the broadcast address establishes a pair wise data link with the other. 
     In contrast to the two-party embodiment, wherein the parties call each other, if there are three or more parties then the parties call in to the bridge  115 . In this embodiment, the bridge  115  may be satisfied by a commercially available conference calling bridge. If the digital network  112  is a routed network, when a device  170  joins the POTS connection and the other devices receive the joining device&#39;s network address, this effectively establishes a data link in that the joining device is now reachable by each of the other participating devices. If the digital network supports persistent, dedicated data links between devices, each of the devices receiving the broadcast address establishes a pair wise data link with the joining device. 
     Acoustic Signals  506   a  (Rendezvous Server Employed) 
     As an alternative to the preceding example, which does not employ the rendezvous server  114 , step  506   a  may be implemented using the rendezvous server  114  while retaining the acoustic signal feature. 
     Here, the parties setup the POTS call as described above. Then, the devices  170  decide upon and then exchange a unique identifier (ID) over the POTS call. This can but need not be a network address, and in fact, the unique ID may be a preassigned user name or password or other unique code. The network address is not necessary at this point because the server  114  facilitates completion of the data link instead of the parties directly exchanging network addresses. Here, the POTS call is used to exchange the unique ID. 
     In one example, the unique ID is determined based on applying a predetermined computation to the current date or time, so that all parties come up with the same unique ID. Or, the device of the first party to join the POTS call may choose the unique ID, or submit a unique ID pre-assigned to that party. In another example, instead of a common unique ID among all parties, every party has a pre-assigned unique ID and each party submits its own unique ID and obtains the unique IDs of every other party. There are many other ways to resolve the unique ID. 
     The rendezvous server  114  has a known or published or ascertainable address on the network  112  so as to be readily accessible by the parties&#39; devices. Accordingly, each party&#39;s device  170  contacts the rendezvous server  114  at a predetermined network address, provides the unique ID or IDs, obtained from the other party via the acoustic signal superimposed over the POTS call, and requests the server to open a data link with the other parties. The server  114  identifies matching requests and establishes a data link between the participating devices. The manner of establishing the data link is discussed in greater detail below. 
     The action of the rendezvous server  114  is described, in a more specific example, as follows. In this example, the server  114  maintains rendezvous data links that any number of parties may join. Here, the server  114  facilitates a new addition to the data link upon receipt of symmetric requests in which (1) A requests to join a data link, (2) A requests that B be added to its data link, (3) B requests to join a data link, and (4) B requests that A be added to its data link. Or, the server adds a device to an existing data link upon receipt of asymmetric requests in which (1) C requests to join a data link, and (2) one or more of D, E, . . . N request that C be added to their existing data link. This may be implemented in different ways. For example, the operation of C&#39;s device contacting the rendezvous server  114  may be automatic or it may be conditioned on one existing party&#39;s approval of C conveyed via their interface  177 , or conditioned on approval of all existing parties to the data link as conveyed via their respective interfaces  177 . 
     If desired, step  506   a  may be implemented to allow subsequent parties to join the existing data link in an unconfirmed manner. That is, the server  114  does not require that another party invite the subsequent party to join the data link. This party&#39;s act of supplying the unique ID already validates the new party. 
     As with the non-server example given above, the devices may transmit the acoustic information using conventional acoustic encoding schemes or less intrusive audio. For example, each party&#39;s device may steganographically encode the information within a synthesized voice announcing the identity of that party. In the case of a three or more parties, this announcement may occur when a party joins the POTS connection. 
     If this embodiment, using acoustic signals and the rendezvous server  114 , is be carried out for three or more parties, parties setup the POTS call by calling in to the bridge  115 . 
     Caller ID  506   b    
     In the embodiment of step  506   b , the server  114  facilitates the data link, but caller ID information obtained via the POTS call (or calls) is used to identify a party (or parties) to the server  114 , as discussed below. The rendezvous server  114  has a known or published or ascertainable address on the network  112  so as to be readily accessible by the parties&#39; devices. 
     This approach differs from the embodiment of  506   a  in that it (1) does not overlay acoustic signals to an ongoing POTS call to help in setting up the data link, and (2) requires participation of the server  114 . Furthermore, the mechanism for connecting multiple parties is different. 
     In the two-party example, the parties first establish a POTS call. Then, the following events take place, automatically or in response to user approval conveyed via the interface  177 . The calling party  106  submits the following data to the rendezvous server  114 : (A) the calling party  106 &#39;s own telephone number, which is pre-programmed into the device  170 , and (B) the called party  108 &#39;s telephone number, which is known to the CPU  170 , by monitoring the user&#39;s operation of the telephone keypad  175 . The called party  108  submits the following data to the rendezvous server  114 : (A) the called party&#39;s own telephone number, pre-programmed into the device  170 , and (B) the calling party&#39;s telephone number, known to the CPU  170  by monitoring the incoming call an detecting the caller ID or other CNID code. The parties may also submit their respective network addresses, or the rendezvous server  114  may detect them automatically upon connection to the server. 
     The rendezvous server  114  receives the parties requests, cross-references the received telephone numbers, and recognizes that calling party  106  seeks a digital link with called party  108 , and vice versa. In response, the server  114  helps establish a data link between the parties, the details of which are explained below. 
     In order to accommodate three or more parties, step  506   b  uses a proprietary conference calling bridge (implemented at  115 ), capable of distinguishing and recording caller-ID codes from each party that calls in. In a different example, to accommodate three or more parties, a new party must place a POTS call to one of the current participants in the data link. Then, the communication devices of the calling party and called party communicate with the rendezvous server  114  in the same manner as discussed above, except that the server  114  functions to add the new party to the data link instead of setting up a new data link. 
     In the proprietary conference calling bridge implementation, the parties need not use the devices  150 ,  170 . In contrast, this example may be carried out for a given party by using a telephone and a computer programmed with the network address of the rendezvous server  114 . 
     In the embodiment with three or more parties, the addition of the new party to the data link may be implemented in different ways. For example, this may occur automatically, or it may be conditioned on an existing party&#39;s approval of the new party conveyed via the interface  177 , or it may be conditioned on approval of all existing parties to the data link as conveyed via their respective interfaces  177 . 
     For instance, the rendezvous server  114  may establish a data link upon receipt of symmetric requests in which (1) A requests to join a data link, (2) A requests that B be added to its data link, (3) B requests to join a data link, and (4) B requests that A be added to its data link, and the server adds a device to an existing data link upon receipt of asymmetric requests in which (1) C requests to join a data link, and (2) one or more of D, E, . . . N request that C be added to their existing data link. 
     Soundprint  506   c    
     The alternative of step  506   c , like the alternative  506   b , does not introduce machine-readable acoustic signals to an ongoing POTS call to set up the data link. Rather, in this alternative, the devices  170  computationally analyze acoustic content of the POTS call to create a soundprint. This takes place automatically or in response to user approval conveyed via the interface  177 . The timing or duration of the analyzed content is not critical, as long as both devices  170  use the same or substantially similar formula for computing the soundprint. 
     In this approach, upon joining a POTS connection, each party&#39;s device  170  monitors the conversation to calculate a numeric descriptor of the conversation. The descriptor may, for example, be computed based using a binned FFT or other commonly implemented audio fingerprinting technique. Alternatively, the descriptor may be based upon the conversational pause rate, or word length counting. Word length counting is pause independent and works well in situations where speakers do not interrupt each other. Preferably, to mitigate the effects of latency, pause rates are separately computed for the local and remote speech signals and combined to obtain the descriptor. This approach requires that the descriptor be sufficiently accurate and unique that the likelihood of a random collision between descriptors, i.e., false-positives, either inadvertent or malicious, is remote. If the likelihood of false positives is sufficiently minimized, the likelihood of false negatives can be reduced by allowing the device to submit several descriptors computed using a variety of techniques. 
     In one embodiment, the descriptor is time invariant and robust to variations in line noise or latency between one device and another. To the extent that the descriptor does vary over the length of the POTS connection, e.g., as new devices join the connection, the devices participating in a data link may periodically recompute descriptors and submit them to the server, thereby ensuring that any device joining the POTS connection is successful in joining the data link upon contacting the server. One approach is to compute the fingerprint continuously and update the remote server periodically. 
     Having prepared their soundprints, the parties&#39; devices  170  submit respective requests to the rendezvous server  114  via the network  112 . These request include, at minimum, that parties&#39; respective soundprints. Optionally, the parties may also track the time at which the POTS call was opened, and additionally submit this to the rendezvous server  114 . The parties may further submit their respective addresses on the network  112 , or the rendezvous server may detect them automatically. 
     The rendezvous server  114  receives the parties&#39; requests, and compares each soundprint to a stored database of soundprints received from various parties. The server  114  may use the parties&#39; reported call start times to narrow down the list of soundprints to examine, and speed the comparison. Upon finding requests with matching soundprints, the server  114  helps establish a digital link between the parties that submitted the matching soundprints. 
     In the case of two parties, they employ the soundprint example ( 506   c ) by calling each other directly. If there are three or more parties seeking to form a data link, then the parties may call-in to the bridge  115 . A conventional bridge service may be used here, without requiring any proprietary features. 
     If desired, step  506   c  may be implemented to allow subsequent parties to join the existing data link in an un-confirmed manner. That is, the server  114  does not require that another party invite the subsequent party to join the data link. This party&#39;s act of supplying the valid soundprint already validates the new party. 
     More About Completing the Data Link 
     As mentioned above, the operation  506  involves the parties discovering each other and then the devices  170  connecting via the network  112 . In one embodiment, each device  170  connects directly to the other party&#39;s network address obtained from the other party. Alternatively, the server  114  broadcasts the parties&#39; network addresses to all parties, whereupon the parties can connect to each other directly. 
     Or, the server  114  itself forms a data link between the devices  170 . Here, instead of providing each party with the other party&#39;s network address to complete discovery ( 506 ), the server  114  connects the parties&#39; devices  170  via the server itself. In this embodiment, the server  114  need not relay each party&#39;s network address to the other, since the parties&#39; devices  170  only need the network address of the server  114 . As another approach, the server  114  may initially conduct the data link through itself, and then negotiate a direct connection between the parties as it becomes possible with the passage of time, to conserve resources. 
     Fail-Safe Mode 
     As an alternative to steps  506   a - 506   c , the device  170  device may offer a fail-safe mode of establishing a data link in which the users participating in the POTS connection verbally agree among themselves on a method of establishing the data link. The users may, for example, agree upon a “session ID” for a rendezvous link maintained by the server  114 , or simply exchange their respective network addresses to enable the establishment of pair wise data links. Any such addresses may be acquired via voice recognition or manually entered at via a number pad or keyboard of the interface  177 . 
     Disconnect POTS 
     After the data link is established ( 506 ), the parties may disconnect the POTS connection ( 510 ). Alternatively, the parties may retain the POTS connection for the audio portion of the call, and use the digital link to relay multimedia such as real time video, presentation content, and the like. 
     Operations During Ongoing Data Link 
     In step  512 , during the ongoing data link, the devices  170  may perform additional functions to employ or take advantage of features of the data link. For example, each device  170  may capture a digital image of local users prior to initiation of the POTS connection and transfer the image across the data link for display on remote devices. For POTS connections involving three or more devices, each device determines locally if it is active, based on microphone signal levels, and broadcasts an active status to the remote devices by transmitting an active speaker flag over the data link. Then, each device uses the active speaker flags to locally display images, or visually highlights an already-displayed images, associated with active remote devices, that is, the remote devices at which a user is speaking. Or, each device  170  may analyze the network addresses of data received over the data link to determine which other party or parties are currently speaking, and then display or highlights the user image of each corresponding speaker. In a different example, custom software sends still pictures and voting metadata over the network. 
     In other examples of step  512 , known software packages may use the data link, with some examples including NETMEETING™, LIVEMEETING™, SKYPE™, ICHA™, etc., where the device  170  (in one example) invokes an API to remotely control the software package into connecting automatically. 
     Disconnect 
     When the parties desire, they may disconnect the data link ( 514 ). For instance, the device  170  may be programmed to disconnect in response to a prescribed button push, code sequence, voice command, or other user command received at the interface  177 . In response, the device  170  directs the interface  176  to drop the digital link with the other party. 
     As to the POTS connection, if still active, the device  170  may retain it or drop it (step  516 ) automatically or upon user input. In one example, the devices may automatically disconnect their data links (step  514 ) in response to sensing that their POTS connections have disconnected ( 516 ). Thus, in this example, the party can disconnect completely by hanging up the POTS connection. 
     Security Enhancements 
     Optionally, the foregoing process may be supplemented by a number of security techniques. For example, upon initially joining a data link, the server  114  may prompt a joining device  170  for a passcode or password. 
     Furthermore, the sequence  500  may employ a two-factor authentication, taking advantage of the parallel communications channels, i.e., POTS and the data link. Because call participants have access to two parallel communications channels, i.e., voice and data, this can be used to provide even greater security. In theory, a remote adversary may have tapped the phone or the data connection, but it is less likely that the adversary has access to both channels, especially if they are remote and somewhere in the middle. 
     In this example, one party&#39;s device  170  synthesizes a voice giving a password over the POTS connection, and the remote parties must enter the password into their respective keypads, thus completing the link loop over the data connection. Alternatively, this may be completely automated with acoustic encodings and the like, with no requirement for the users to do anything. The password requirement is enforced by the server  114  in one implementation, or by the parties&#39; devices  170  in a different implementation. In any case, by automatically asking every communication device that joins the conference to do this, this adds a layer of security to the system. Someone with a laptop and tapping the data connection would not be able to connect unless they had access to the sounds on the POTS line. 
     As another security feature, the devices may employ contents of the data link in computing an authentication token. The computation of the token may be similar to the soundprint computation described above for the voice link. In one embodiment, a device analyzes the sound represented by analog signals sent to the user&#39;s telephone speaker and received by the user&#39;s telephone microphone, received via analog-to-digital converter built into a component such as  158  or  179 . In a different embodiment, a device reconstructs and analyzes transmitted and received data packets to determine the sound of the conversation, and analyzes the resultant sound. 
     By comparing the soundprint calculated for a past conversation with other users, the parties can confirm that their conversation took place as they assumed. This is analogous to each party having a checksum or error correction code for the data link communications, and as long as each party&#39;s checksum matches the other parties&#39; checksums, the conversations are intact. In this example, the devices  170  may present the respective party with a real-time, ongoing token for this purpose, or compute a comprehensive token after the call. If done after the fact, it may be particularly beneficial to compute the token based on all, or substantially all, of the conversation, to avoid the scenario where some of the conversation is omitted from the token and therefore subject to undetected tampering. The devices  170  may automatically or manually present the tokens to the respective users, or after the parties&#39; request to terminate the data link, negotiate with the other devices to compare tokens and present the results to the respective parties. Other variations and adaptations of this core teaching will be apparent to ordinarily skilled artisans, having the benefit of this disclosure. 
     Other Embodiments 
     While the foregoing disclosure shows a number of illustrative embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims. Accordingly, the disclosed embodiment are representative of the subject matter which is broadly contemplated by the present invention, and the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims. 
     Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 USC. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the phrase “step for.” 
     Furthermore, although elements of the invention may be described or claimed in the singular, reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but shall mean “one or more”. Additionally, ordinarily skilled artisans will recognize that operational sequences must be set forth in some specific order for the purpose of explanation and claiming, but the present invention contemplates various changes beyond such specific order.