(12) United States Patent
`Guy et al.
`
`111111111111111111111111111111111111111111111111111111111111111111111111111
`US006298057Bl
`US 6,298,057 Bl
`*Oct. 2, 2001
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) SYSTEM AND METHOD FOR RELIABILITY
`TRANSPORTING AURAL INFORMATION
`ACROSS A NETWORK
`
`(75)
`
`Inventors: Kenneth R. Guy, Thousand Oaks;
`Jaswant R. Jain, Chatsworth; Ishwar
`V. Jasuja, Simi Valley; Michael W.
`Johnson; Albert Juandy, both of
`Petaluma; Simon S. Lam, Agoura Hills;
`Anthony Y. Lee, Northridge; David
`Misunas, Thousand Oaks; Jacques A.
`Roth, San Rafael, all of CA (US)
`
`(73) Assignee: Norte) Networks Limited, St. Laurent
`(CA)
`
`( *) Notice:
`
`This patent issued on a continued pros(cid:173)
`ecution application filed under 37 CFR
`1.53( d), and is subject to the twenty year
`patent term provisions of 35 U.S.C.
`154(a)(2).
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 08/634,927
`
`(22) Filed:
`
`Apr. 19, 1996
`
`(51)
`
`Int. CI? .............................. H04L 12/28; H04J 3/16;
`G06F 11!00
`(52) U.S. Cl. .......................... 370/389; 370/466; 370/474;
`714/746
`(58) Field of Search ..................................... 370/359, 389,
`370/401, 402, 403, 405, 419, 450, 466,
`467, 473, 474, 477; 371/31, 30; 395/182.18;
`348/466; 714/746, 747
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`4,630,262 * 12/1986 Callens et a!. ....................... 370/435
`4,726,019 * 2/1988 Adelmann eta!. .................. 370/474
`4,866,704 * 9/1989 Bergmann ............................ 370/452
`2/1993 Guy eta!. .
`5,187,591
`5,341,374 * 8/1994 Lewen eta!. ........................ 370/450
`
`5,359,598 * 10/1994 Steagall et a!. ...................... 370/359
`5,394,407
`2/1995 Coddington ......................... 371/37.1
`5,426,652
`6/1995 Heiman .................................. 371/30
`5,459,741
`10/1995 Iwamura ............................. 371/37.1
`5,596,604
`1!1997 Cioffi et a!. .......................... 345/260
`6/1997 Huang et a!. ....................... 371/37.1
`5,636,231
`5,659,541 * 8/1997 Chan .................................... 370/236
`5,699,485 * 12/1997 Shoham .............................. 395/2.32
`
`OTHER PUBLICATIONS
`
`Request for Comments (RFC) 2205, Resource ReSerVation
`Protocol-Version 1 Functional Specification, dated Sep.
`1997.
`* cited by examiner
`
`Primary Examiner-William Luther
`(74) Attorney, Agent, or Firm-Trap, Pruner & Hu, P.C.
`
`(57)
`
`ABSTRACT
`
`A system and method for transparently transmitting aural
`signals across a wide area network (WAN). The system of
`present invention is connected to one or more of a private
`branch exchange, a key telephone system, a telephone, a
`facsimile machine, and a modem, for example. In the case
`of voice transmission, a user places a telephone call using
`the same procedure that is used when placing a telephone
`call over a conventional public switched network. The aural
`signals are translated into a format that is compatible with
`the local area network (LAN) and the translated signals are
`transmitted to a router or a switch that connects the LAN to
`the WAN. The data is transmitted across the WAN to a router
`or switch coupled to a second LAN. The data is then sent to
`a destination central site unit or PC which translates the
`signal into a format that is compatible with the telephone
`system connected thereto. The present invention provides a
`voice quality that approaches, equals, or exceeds the voice
`quality of conventional telephone switched networks. This
`high voice quality is achieved by utilizing a high quality
`voice digitization algorithm, by ensuring a low maximum
`network delay, by dynamically compensating for variations
`in network delay, and by using a forward error correction
`technique that can recreate lost or delayed signals in a
`manner that recreates the signal so the lost signal is typically
`not detectable by a user.
`
`36 Claims, 9 Drawing Sheets
`
`FEC3
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`
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`
`F2B' I F1B'
`
`Recreated Voice Packet
`
`FEC2
`
`F2B I F1B
`
`Packet 8
`
`RingCentral Ex-1032, p. 1
`RingCentral v. Estech
`IPR2021-00574
`
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`RingCentral Ex-1032, p. 2
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`RingCentral Ex-1032, p. 3
`RingCentral v. Estech
`IPR2021-00574
`
`

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`RingCentral Ex-1032, p. 4
`RingCentral v. Estech
`IPR2021-00574
`
`

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`RingCentral Ex-1032, p. 5
`RingCentral v. Estech
`IPR2021-00574
`
`

`

`U.S. Patent
`
`Oct. 2, 2001
`
`Sheet 5 of 9
`
`US 6,298,057 Bl
`
`No
`
`Determine Destination
`ChanneVPhoneiD
`
`512
`
`Transmit Call Request
`Packet to Destination
`Server with Call
`Parameters
`
`518
`
`Yes
`
`Reserve Network
`Bandwidth using RSVP
`Protocol
`
`Ring Phone or Transmit 532
`Dialed Digits to Through
`Destination Channel
`
`Figure 5
`
`RingCentral Ex-1032, p. 6
`RingCentral v. Estech
`IPR2021-00574
`
`

`

`U.S. Patent
`
`Oct. 2, 2001
`
`Sheet 6 of 9
`
`US 6,298,057 Bl
`
`Receive Signal from PBX/
`Phone/KTS/Fax/Modem
`
`602
`
`Convert to PCM Signal
`
`Identify Type of Signal
`
`610
`
`Load Fax or Modem Modules No
`If Not Already In Memory
`
`Process Signal
`
`Load Voice Modules Into
`DVM Memory If Not Already
`in Memory
`
`Compress Voice Signal
`
`622
`
`Determine FEC information
`
`626
`
`Modify Data Rate
`
`Create Frame
`
`Figure 6A
`
`RingCentral Ex-1032, p. 7
`RingCentral v. Estech
`IPR2021-00574
`
`

`

`U.S. Patent
`
`Oct. 2, 2001
`
`Sheet 7 of 9
`
`US 6,298,057 Bl
`
`Transmit Packet to
`Destination Server/PC
`
`632
`
`No
`
`Load Fax or Modem Modules 636
`if Not Already in Memory
`
`Load Voice Modules if Not
`Already in Memory
`
`Process Signal
`
`638
`
`Measure Network Delay/
`Dynamically Adujst Jitter
`Buffer
`
`648
`
`Recreate Packet
`
`Decompress Voice Signal
`
`Convert to Analog Signal
`
`Transmit to Phone/Fax/KTS/
`Modem/PBX
`
`Figure 68
`
`RingCentral Ex-1032, p. 8
`RingCentral v. Estech
`IPR2021-00574
`
`

`

`U.S. Patent
`
`Oct. 2, 2001
`
`Sheet 8 of 9
`
`US 6,298,057 Bl
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`RingCentral v. Estech
`IPR2021-00574
`
`

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`RingCentral v. Estech
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`

`

`US 6,298,057 Bl
`
`1
`SYSTEM AND METHOD FOR RELIABILITY
`TRANSPORTING AURAL INFORMATION
`ACROSS A NETWORK
`
`RELATED APPLICATIONS
`
`This application is related to U.S. patent application Ser.
`No. 08/666,800 filed on Jun. 19, 1996 now U.S. Pat. No.
`5,790,641 titled "System and Method for Improving Fac(cid:173)
`simile Delay Tolerances", to U.S. patent application Ser. No.
`08/724,655, filed on Oct. 1, 1996 titled "System and Method
`for Transmitting Aural Information Between a Computer
`and Telephone Equipment", and to U.S. patent application
`Ser. No. 09!059,635 filed on Apr. 13, 1998 titled "System
`and Method for Improving Facsimile Delay Tolerances".
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates generally to the field of
`telecommunications and more particularly to the field of
`transmitting aural information through a wide area network.
`2. Description of Background Art
`Conventional aural communication is accomplished using
`a public switched network, e.g., the telephone network.
`Through the use of such a public switched network users can
`easily communicate with each other by transmitting aural
`signals from a first terminal to a second terminal through the
`public switched network. The aural signals can represent
`voice data, modem data, or facsimile (fax) data, for example.
`In order to transmit voice data, a user performs a conven(cid:173)
`tional procedure for setting up a call, and for tearing-down
`a call. In one example of a conventional call setup
`procedure, a user lifts a handset on a first telephone, listens
`for a dial-tone, and then enters a code identifying a desti(cid:173)
`nation telephone. A user at the destination telephone is
`notified that a connection is pending, e.g., by hearing the
`destination telephone ring, and the user lifts the handset.
`After the handset of the destination telephone is lifted, a
`connection between the first telephone and the destination
`telephone is established. As each user speaks, the sound is
`transformed and then transmitted through the telephone,
`through a private branch exchange (if any), through the
`public switched network, and then to the destination tele(cid:173)
`phone where the transformed signal is re-transformed into
`an audible signal that can be heard by the user at the
`destination telephone.
`Recently, communication systems have been developed
`that enable aural data to be transmitted over a wide area
`network (WAN). In these systems a private branch exchange
`(PBX) is connected to a communication device, e.g., a 50
`router, switch, FRAD, or multiplexor, that connects two
`networks having different data formats, e.g., a local area
`network (LAN) and a WAN. An example of a data format is
`a packet. A packet is a group of bits having a header portion
`and a data portion. The format of a packet can be different 55
`for each LAN and WAN. For example, the maximum size of
`a packet and packet destination and routing information can
`differ between networks. A router or a switch, hereafter
`referred to as a router, that also handles aural data converts
`a packet from a first format that is compatible with the PBX 60
`to a second format that is compatible with a WAN. After
`receiving the aural signals from the PBX, the router converts
`the aural signals into packets, transmits the packets across a
`WAN where they are received by a second router that is
`connected to a second PBX, key system or telephone. The 65
`second router converts the packets into aural signals and
`transmits the signals to the PBX, key system or telephone.
`
`2
`There are problems with connecting a source of aural
`information directly to a router. One problem is that the
`format of aural information and the format of information
`that can be received by the network router are typically
`incompatible and, in general, a specially developed router
`must be used to enable the PBX to transmit data through a
`WAN. A second problem is that routers are, typically, not
`capable of being inexpensively modified to receive tele(cid:173)
`phony functionality, for example, it is difficult to add a
`10 circuit board having the required telephony functionality to
`a router. Accordingly, in order to add telephony compatibil(cid:173)
`ity and functionality to a WAN, a WAN user must replace the
`existing routers. This is an expensive solution. A third
`problem is routers that are compatible with a PBX or a KTS
`15 generally provide proprietary solutions that are not compat(cid:173)
`ible with those of other routers. A fourth problem is that such
`solutions are not generally available in routers, thus limiting
`the options of a user.
`Another technique for transmitting aural signals across a
`20 WAN is to connect a microphone and a speaker to a
`conventional personal computer (PC). A user loads and
`executes a software program that converts the received
`analog signal to a digital signal using the processor in the
`PC. The signal may be sent over a LAN to a router. The
`25 router transmits the signal over a WAN to a second router.
`The second router may transmit the signal over a second
`LAN, or directly, to a destination PC. If the destination PC
`is operating compatible software, the PC can convert the
`received signal back to an audible signal that is transmitted
`30 through the PC's speakers. While this technique is less
`expensive than the first technique, it also has limitations.
`One limitation is that such systems are currently incapable
`of providing a priority mechanism that would ensure that
`aural data arrives within a predetermined maximum time
`35 period. Most data currently transmitted through WANs are
`not time sensitive, i.e., a small delay in receiving data is
`acceptable if the data is accurate. However aural commu(cid:173)
`nication is time sensitive, i.e., it is generally more important
`for aural data to be received in a timely manner than it is for
`40 the data to be absolutely accurate. If, while a user is speaking
`into a microphone, another computer that is coupled to a
`router via the LAN requests a transfer of a large file, e.g., a
`computer aided design (CAD) file, the packets of voice data
`that are received by the first router after the first router
`45 begins transmitting the packets of the CAD file may incur a
`significant delay if the router transmits all of the packets of
`the CAD file before transmitting the aural packets. In this
`situation, the second user will experience a significant delay
`in the reception of aural signals.
`A second limitation is that due to limitations on host
`processing capability, the quality of the received aural signal
`is significantly degraded when compared to the transmitted
`aural signal and cannot be characterized as a toll-quality or
`near-toll-quality signal. The public switched networks in the
`industrialized countries provide a toll-quality signal. A near(cid:173)
`toll-quality-signal is within 0.5 point of the toll-quality
`signal as measured by the means-opinion-score (MOS)
`method, on a scale of five, as determined by listening tests.
`A signal that is 1.0 point below the toll-quality signal is
`generally characterized as a communications-quality signal.
`The MOS method is described in greater detail in ITU-T
`Recommendation P.83, Subjective Performance Assessment
`of Telephone-Band and Wide band Digital CODECS, (March
`1993), that is incorporated by reference herein in its entirety.
`A third limitation is that the software for converting an
`analog aural signal from the microphone into an aural packet
`that is compatible with the LAN requires significant com-
`
`RingCentral Ex-1032, p. 11
`RingCentral v. Estech
`IPR2021-00574
`
`

`

`US 6,298,057 Bl
`
`4
`data-network; (2) transparently generating and rece1vmg
`aural data; (3) incorporating a robust error correction pro(cid:173)
`cedure that enables a receiver to recreate lost data; ( 4)
`converting aural signals into a network compatible format,
`and performing compression and decompression algorithms
`on the converted data without placing a significant compu(cid:173)
`tationalload on a host processor; (5) utilizing a router/switch
`priority system to minimize the end-to-end packet delay
`across a wide area network; (6) adjusting the destination
`10 signal based upon packet delay variations; (7) communicat(cid:173)
`ing with a router/switch over a standard LAN connection
`without requiring a specialized router/switch voice inter(cid:173)
`face; and (8) connecting to a LAN with a standard interface
`and communicating over the LAN in standard data formats.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`3
`putational power that is provided by the processor in the PC.
`As a result of this additional computational load on the
`processor, the processing capability of the computer that is
`available for processing other application programs, is sig(cid:173)
`nificantly reduced.
`A fourth limitation is that the call setup and conversation
`between two users is not transparent. That is, the quality of
`the received signal is not at a near-toll-quality standard, and
`the procedures used to initiate the connection and to main(cid:173)
`tain the connection are not conventional. Instead of lifting a
`handset, listening for a dial-tone, and entering a destination
`identifier on a telephone keypad, the user executes a soft(cid:173)
`ware program, types a destination identifier using a com(cid:173)
`puter keyboard and then talks into an external microphone
`and listens though speakers attached to the PC. Similarly, to
`receive the audible signals, the user must, for example, 15
`execute a software program, use a mouse to click on an
`"answer" button, and turn on the speakers. This lack of
`transparency requires users to re-learn how to communicate
`with a person at a remote location.
`Accordingly, what is needed is a system and method: (1) 20
`for transmitting aural information as digital signals over a
`wide-area-data-network; (2) for transparently generating
`and receiving aural data; (3) that incorporates a robust error
`correction procedure that enables a receiver to recreate lost
`data; ( 4) that converts aural signals into a network compat- 25
`ible format, and that performs compression and decompres(cid:173)
`sion algorithms on the converted data without placing a
`significant computational load on a host processor; (5) that
`uses a router/switch priority system to minimize the end-to(cid:173)
`end packet delay across a wide area network; (6) that adjusts 30
`the destination signal based upon packet delay variations;
`(7) that communicates with a router/switch over a standard
`LAN connection without requiring a specialized router/
`switch voice interface; and (8) that can connect to a LAN
`with a standard interface and can communicate over the
`LAN in standard data formats.
`
`FIG. 1 is an illustration of a computer network environ(cid:173)
`ment in which the preferred embodiment of the present
`invention operates.
`FIG. 2 is a more detailed illustration of a PC/file server,
`and a phone/fax server card installed therein, having an
`analog telephony interface according to the preferred
`embodiment of the present invention.
`FIG. 3 is a more detailed illustration of a digital voice
`module component of the phone/fax server card according to
`the preferred embodiment of the present invention.
`FIG. 4 is a more detailed illustration of a PC/file server
`memory module according to the preferred embodiment of
`the present invention.
`FIG. 5 is a flow chart illustrating a call setup procedure
`according to the preferred embodiment of the present inven(cid:173)
`tion.
`FIGS. 6A and 6B are flow charts illustrating an aural
`35 signal transmission procedure according to the preferred
`embodiment of the present invention.
`FIG. 7 is an example of the forward error correction
`(FEC) process illustrating three voice packets, packet A,
`packet B, and packet C.
`FIG. 8 is a more detailed illustration of a PC/file server
`and a phone/fax server card having a digital telephony
`interface according to an alternate embodiment of the
`present invention.
`
`40
`
`SUMMARY OF THE INVENTION
`The invention is a system and method for transparently
`transmitting aural signals across a wide area network
`(WAN). The system of present invention is quickly and
`inexpensively installed in a server or a personal computer
`coupled to a local area network. The system is connected to
`one or more of a private branch exchange, a key telephone
`system, a telephone, a facsimile machine, and a modem. In 45
`the case of voice transmission, a user places a telephone call
`using the same procedure that is used when placing a
`telephone call over a conventional public switched network.
`The aural signals are translated into a format that is com(cid:173)
`patible with the local area network (LAN) and the translated 50
`signals are transmitted to a router or a switch that connects
`the LAN to the WAN. The data is transmitted across the
`WAN to a router or switch coupled to a second LAN. The
`data is then sent to a destination central site unit or PC which
`translates the signal into a format that is compatible with the
`telephone system connected thereto. The present invention
`provides a voice quality that approaches, equals, or exceeds
`the voice quality of conventional telephone switched net(cid:173)
`works. This high voice quality is achieved by utilizing a high
`quality voice digitization algorithm, by ensuring a low
`maximum network delay, by dynamically compensating for
`variations in network delay, and by using a forward error
`correction technique that can recreate lost or delayed signals
`in a manner that recreates the signal so the lost signal is
`typically not detectable by a user.
`The benefits of the present invention include: (1) trans(cid:173)
`mitting aural information as digital signals over a wide-area-
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`A preferred embodiment of the present invention is now
`described with reference to the figures where like reference
`numbers indicate identical or functionally similar elements.
`Also in the figures, the left most digit of each reference
`number corresponds to the figure in which the reference
`number is first used.
`FIG. 1 is an illustration of a computer network environ-
`55 ment in which the preferred embodiment of the present
`invention operates. FIG. 1 illustrates a first local configu(cid:173)
`ration 102Acoupled to a second local configuration 102B by
`a wide area network (WAN) 104. The first and second local
`configurations include a router 114, 132, file servers or
`60 personal computers (PCs) 112, 122, 130, and local area
`networks (LAN) 116, 134. Examples of LANs include an
`ethernet and a token ring network, an examples of a WAN
`include leased lines, frame relay, asynchronous transfer
`mode (ATM) networks, and the Internet. The present inven-
`65 tion enables a user to transmit aural signals across a WAN
`using conventional telephones, facsimile machines (fax),
`and modems, i.e., in a transparent manner. It will be apparent
`
`RingCentral Ex-1032, p. 12
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`IPR2021-00574
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`US 6,298,057 Bl
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`5
`to persons skilled in the relevant art that the present inven(cid:173)
`tion can operate on many different types of LANs and WANs
`without departing from the scope of the present invention.
`The first local configuration 102A includes two telephones
`106, 108 coupled to a key telephone system (KTS) 110. In
`the present invention, the KTS 110 is coupled to a phone/fax
`server card (PFSC) located on a PC or a file server 112 via
`signal lines 107. In the preferred embodiment, the PFSC is
`located on a server. Accordingly, the description of the PFSC
`will be with respect to a file server. As described below, in
`an alternate embodiment, the PFSC is configured in a PC or
`other host processor system. The file server 112 and PFSC
`are described in greater detail below. The file server 112 is
`connected to the LAN via a network interface 113. The
`network interface 113 is coupled to the router 114 via the
`LAN 116. The router 114 receives data from devices in the
`first local configuration 102A, e.g., the file server 112. The
`data can be in the form of packets, as described below. The
`router transmits the packets from the local configuration
`102A to the WAN 104 and then the packets are routed
`through the WAN 104 to a second router 132 in the second
`local configuration 102B. In an alternate embodiment of the
`present invention, a network switch or hub can be used in
`conjunction with, or in place of, the routers 114, 132.
`The second local configuration 102B includes a second
`file server 122 having a phone/fax server card that is coupled
`directly to a telephone 118 and to a fax 120. The second
`LAN 102B is also coupled to a phone/fax server central site
`unit (CSU) 130. The CSU 130 is a PC that only performs
`operations related to the operation of the one or more
`phone/fax server cards located therein. The CSU 130 can
`contain multiple cards and is, generally, more reliable than
`either stand alone PCs or file servers because PCs and file
`servers typically also perform operations and run application
`programs not related to the PFSC. The CSU 130 is coupled
`to a conventional private branch exchange (PBX) 128 which
`in turn can be coupled to many telephones or faxes. In FIG.
`1, two telephones 124, 126 are connected to the PBX 128.
`The second local configuration 102B includes a network
`interface 123 that is communicates through the LAN 134 to
`the router 132, the second file server 122, the CSU 130, and
`the remaining devices attached to the LAN 134. The second
`local configuration 102B is an example of a LAN connecting
`multiple devices, for example, each server 122, 130 can be
`connected to a hub in a different building.
`The present invention is a system and method for enabling
`aural signals, e.g., voice signals, facsimile (fax) signals, and
`modem signals, to be transparently generated and transmit(cid:173)
`ted to a phone/fax card located in a file server 112 coupled
`to a computer network or in a personal computer coupled to 50
`a first local configuration 102A. The file server 112 performs
`a setup operation to prepare a connection between two aural
`signal generation devices, e.g., between the first telephone
`106 in the first local configuration 102A and the second
`telephone 126 in a second local configuration 102B. After 55
`setting up the connection, the PFSC in the file server 112
`converts the received aural signals into digital signals and
`compresses the digital signals. Packets are generated from
`the compressed digital signals and these packets are trans(cid:173)
`mitted to the router 114 via the LAN 116. The router 60
`transmits the packets across a wide area network (WAN),
`e.g., leased lines, frame relay, or the Internet, and the packets
`are received by the second router 132 in the second local
`configuration 102B. The second router 132 transmits the
`packets to the destination CSU 130. The destination CSU 65
`130 converts the compressed digital signals in the packet
`into aural signals and transmits the aural information to the
`
`6
`PBX 128 which transmits the signal to the second telephone
`126. A more detailed description of the operation of the
`present invention is set forth below.
`The present invention provides a cost-effective system
`and method for transmitting aural information from an aural
`signal generating device that is connected to a first local
`configuration 102A to an aural signal receiving device, e.g.,
`the second telephone 126, connected to a second local
`configuration 102B, where the first local configuration 102A
`10 and the second local configuration 102B are both connected
`by a WAN 104. As described above, an aural signal gener(cid:173)
`ating device and an aural signal receiving device can be, for
`example, a telephone, a fax, or a modem. The present
`invention can reside in a server 112 or in a personal
`15 computer, for example. In contrast, previous systems couple
`a PBX, key system, or telephone, directly to a router 114.
`Routers are typically designed such that the user does not
`have the capability to add functionality thereto, other than
`that functionality provided by the manufacturer of the router.
`20 Accordingly, a router designer and manufacturer must
`include the aural transmission capability in the router. The
`user is thereby unable to modify an existing LAN environ(cid:173)
`ment to add voice communication capability without replac(cid:173)
`ing the existing routers at a significant additional expense.
`25 The present invention enables a user of a LAN/WAN
`network to quickly and inexpensively add a near-toll-quality,
`transparent, aural transmission system to a network by
`installing hardware and software in a PC that are coupled to
`a LAN in the network. As described above, previous
`30 attempts at providing such functionality have provided solu(cid:173)
`tions that are of lesser quality and are generally not accept(cid:173)
`able for business use because the quality of the aural signal
`was low and the interface with the users was not transparent.
`In the preferred embodiment, the present invention
`35 includes a phone/fax server card (PFSC) that is controlled by
`software, as described below. Preferably, the PFSC is
`located in one PC, one file server 112, or a dedicated CSU
`130 per office or LAN site. File servers 112, or a CSU 130
`are typically always operating. In contrast, a PC is generally
`40 less available because a user may turn off the PC or operate
`less robust programs than on a server 112 which can cause
`the PC to fail. However, in an alternate embodiment, one or
`more PFSCs can be installed in a PC that is connected to a
`LAN, e.g., for use in an office without a server on the LAN.
`45 For ease of discussion, the description set forth below will
`describe a telephone call between a user at a first telephone
`106 and a user at a second telephone 126 wherein the user
`of the first telephone initiated the call and where the first
`telephone 106 is coupled to a file sever 112 via a KTS 110
`and the second telephone is coupled to the CSU 130 via a
`PBX 128.
`FIG. 2 is a more detailed illustration of a file server 112
`and a PFSC 202 having an analog telephony interface
`according to the preferred embodiment of the present inven(cid:173)
`tion. With respect to the present invention, the CSU 130, the
`second file server 122, and a PC (not shown) each has a
`PFSC 202, and each operates in substantially the same
`manner as the file server 112. Any distinctions between the
`operation of the present invention and any of these devices
`are apparent to persons skilled in the relevant art. The file
`server 112 can be a conventional PC that is utilized as a file
`server. The file server 112 includes a network interface card
`(NIC) 218, a processor 216, a server memory module 214,
`and a PFSC 202. The NIC 218 can be a conventional NIC,
`for example, a 3C509 NIC that is commercially available
`from 3Com Corp., Santa Clara, Calif. The NIC 218 converts
`signals from the file server 112 into a format used by the
`
`RingCentral Ex-1032, p. 13
`RingCentral v. Estech
`IPR2021-00574
`
`

`

`US 6,298,057 Bl
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`7
`LAN 116. A benefit of the prese