PCT
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`INTERNATIONAL APPUCA TION PUBUSHED UNDER TilE PATENT COOPERATION 1REA TY (PCT)
`(51) International Patent Classlftcatioo 6:
`WO 96/23377
`(11) International PubUcatlon Number:
`H04L 11110, H04Q 11104, H04M 19/08
`
`A1
`
`•
`
`(43) International Publication Date:
`
`I August 1996 (01.08.96)
`
`(ll) International AppUc:atlon Number:
`
`PCT/1896/00223
`
`(ll) International Filing Date:
`
`26 January 1996 (26.01.96)
`
`(30) Priority Data:
`08/379,365
`
`27 January 1995 (27.01.95)
`
`us
`
`(71) AppUcant:
`INTECOM, INCORPORATED [US/US]; 5057
`Keller Springs Road, Dallas, TX 75248 (US).
`
`(81) Designated States: AL, AM, AT, AU, AZ, BB, BG, BR, BY,
`CA, CH, CN, CZ. DE, DK, EE, ES, Fl, OB, OE, HU, IS,
`JP, KE, KG, KP, KR, KZ, LK, LR, LS, LT, LU, LV, MD,
`MG, MK, MN, MW, MX, NO, NZ, PL. PT, RO, RU, SO,
`SE, SG, Sl, SK, TJ, TM, TR, TI, UA, UG, UZ, VN, ARIPO
`patent (KE, LS, MW, SD, SZ, UG), Eurasian patent (AZ,
`BY, KG, KZ, RU. TJ, TM), European patent (AT, BE, CH,
`DE, DK, ES, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE),
`OAPJ patent (BF, BJ, CF, CG, CJ, CM, GA. GN, MI.., MR,
`NE, SN, TD, TG).
`
`(7l) Inventors: HUNTER, Richard, K.; Apartment 804, 4815 Published
`Westgrove Road, Dallas, TX 75248 (US). PLATI, Richard,
`With international search report.
`B.; 1111 Ashby Drive, Allen, TX 75002 (US).
`Before the expiration of tire time limit for amending tire
`cklim.s and to be republislred in tire event of tire receipt of
`amendments.
`
`(74) Agent: HITI, David, H.; Hitt Chwang & Gaines, P.C., Suite
`225, 275 West Campbell Road, Richardson, TX 75080 (US).
`
`(54) 11tle: MULTIMEDIA SYSTEM HAVING CENTRAL POWER SOURCE AND DISTRIBUTION SUBSYSTEM
`
`(57) Abstract
`
`A power subsystem and method for providing phantom power and third pair power via a computer network bus, the bus including
`first and second conductors. The phantom power subsystem comprises: (1) a power supply having a positive output and a negative output,
`the power supply adapted to provide power via the positive and negative outputs and (2) first and second transformers, each of the first and
`second transformers having a winding, each of the windings having a pair of end taps and a center tap, the first conductor coupled to the
`end taps of the winding of the first transformer to allow data communication therebetween, the second conductor coupled to the end taps
`of the winding of the second transformer to allow data communication therebetween, the positive and negative outputs of the power supply
`coupled to the center taps of the windings of the first and second transformers, respectively, to allow the power supply to transmit the
`power, via the first and second transformers and the first and second conductors, to equipment couplable to the first and second conductors.
`
`~EST AVAILABLE COPY
`
`

`
`FOR THE PURPOSES OF INFORMATION ONLY
`Codes used to identify States party to the PCI' on the front pages of pamphlets publishing international
`applications under the PCT.
`
`AmiCIIia
`AM
`Auatria
`AT
`Aualnlia
`AU
`Bllbldol
`BB
`Belailllll
`BE
`Bwkllla Fuo
`BF
`Baalpria
`BG
`BelliD
`8J
`Bruil
`BR
`Be!uu
`BY
`Cmada
`CA
`Cellini Afric111 Republic
`CF
`Coop
`CG
`Swiu.crlud
`CH
`a
`Cble d"lvoire
`CM c -
`ChiDa
`CN
`cs
`c-hollovatia
`cz
`Cucb Republic
`DE
`Genuay
`DeDmartt
`OK
`l!lloDia
`EE
`SpAin
`ES
`n
`Filllmd
`FR
`Frlllce
`Glial
`GA
`
`Ulliud Kinadom
`GB
`Gecqia
`GE
`OWDca
`GN
`GR a -
`Hquy
`HU
`Ireland
`IE
`l1aly
`IT
`JP
`JapiD
`Jteaya
`KE
`K)'11)'&LIII
`KG
`Democntic: Ptople"a Republic
`KP
`of Korea
`Republic of Korea
`KR
`Kuakbr.l.lll
`KZ
`u
`l..iec:hlelll&ein
`Sri Lanka
`LK
`Uberia
`LR
`Uthaaania
`LT
`Lllxembourl
`LU
`Lalvia
`LV
`MC M -
`Republic of Moldova
`MD
`Madl,guc:e.r
`MG
`Mali
`ML
`Mongolia
`MN
`MR
`Maw:ilania
`
`MW
`MX
`NE
`NL
`NO
`NZ
`PL
`PI'
`RO
`RU
`SD
`SE
`SG
`Sl
`SK
`SN
`sz
`TD
`TG
`TJ
`1T
`UA
`UG
`us
`UZ
`VN
`
`Malawi
`Maic:o
`Nip
`Nelherllnds
`Ncxway
`New Zealalld
`Polmd
`l'l:lrlulal
`Romania
`R1111i&ll Federuion
`Sudan
`s-xa
`Singapo"'
`SlovCIIia
`Slovakia
`Sale pi
`Swu.il.uld
`Chid
`Toao
`Tajitiaun
`Tlinldad and Tobago
`Ukni:De
`U&Uida
`United Staid of America
`Uzbetiaun
`VietNam
`
`

`
`WO'J6/l3377
`
`PCf/IB96/00ll3
`
`1
`
`MULTIMEDIA SYSTEM HAVING CENTRAL POWER SOURCE
`AND DISTRIBUTION SUBSYSTEM
`
`TECHNICAL FIELD OF TliE INVENTION
`
`in general,
`The present invention is directed,
`to a power
`5 multimedia systems and, more specifically,
`subsystem for a multimedia subsystem and a method of
`the
`therefor,
`third pair power
`providing phantom and
`subsystem providing a central power source and distribution
`of power to equipment comprising the system.
`
`to
`
`10
`
`BACKGROUND OF TliE INVENTION
`
`15
`
`CUrrently, "Information superhighway" and "multimedia"
`least often
`the most often spoken and
`are probably
`in data
`revolution
`coming
`a
`understood aspects of
`communication. Although issues specific to an information
`the present
`scope of
`the
`superhighway are beyond
`discussion, interactive multimedia systems are very much
`within the present scope.
`An interactive multimedia system is broadly defined as
`a system capable of processing, storing, communicating and
`20 coordinating data pertaining to visua1 information, aural
`
`

`
`W096/23377
`
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`
`10
`
`2
`information and other information. Visual information is
`generally divided into still: picture or graphics and full
`In the vernacular of
`motion video or animation categories.
`those involved in multimedia, such visual information is
`5 generically referred to as. "video." Aural information is
`generally divided into speech and non-speech categories and
`"Other
`"voice."
`as
`to
`referred
`is generically
`information 11 is directed primarily to computer data, often
`organized in files and records, and perhaps constituting
`Such computer data are
`textual and graphical data.
`generally referred to as "data."
`the most part, been
`for
`To date, multimedia has,
`limited to stand-alone computer systems or computer systems
`("LAN") . While
`linked together in a local area network
`such isolated systems have proven popular and entertaining,
`the true value of multimedia will-become apparent only when
`multimedia-capable wide area networks ("WANs") and protocol
`installed that
`systems are developed, standardized and
`Such multimedia
`interactive multimedia.
`truly
`permit
`systems will allow long distance communication of useful
`quantities of coordinated voice, video and data, providing,
`the voice-only
`to
`a multimedia extension
`in effect,
`services of the ubiquitous telephone network.
`Defining the structure and operation of an interactive
`the
`in
`first step
`a critical
`is
`system
`25 multimedia
`development of such system. Accordingly, before entering
`into a discussion herein of more specific design issues, it
`is important to discuss more general questions that need to
`be resolved concerning design objectives of the system as
`
`15
`
`20
`
`

`
`wo 96113377
`
`PCf/IB96/00223
`
`3
`
`some generally agreed-upon answers
`
`and
`
`a whole and
`specifications.
`thought of as an
`Interactive multimedia may be
`electronic approximation of the · paradigm of interactive
`5 group discussion.
`It involves ·the interactive exchange of
`voice, video and data between two or more people through an
`electronic medium in real time. Because of its interactive
`and real-time nature, there are some stringent requirements
`and
`required
`services not normally associated with
`10 multimedia retrieval systems.
`Some of the more obvious
`examples of those requirements and services include latency
`(transmission delay),· conferencing, availability {"up(cid:173)
`time'') and WAN interoperability.
`The evolution of existing pri va.te branch exchange
`("PBX") and LAN topologies towards a composite interactive
`multimedia system based upon client/server architectures
`and isochronous networks is a natural trend. However, to
`merge
`the disparate mediums of voice, video and data
`successfully into a cohesive network requires that three
`fundamental integration issues be defined and resolved.
`The first of the fundamental integration issues is quality
`of service
`( "QoS") .
`QoS
`is defined as the effective
`communication bandwidth,
`services
`and media quality
`coupling of separate equipment or "terminals" together and
`the availability ("up-time") of the same. QoS parameters
`are divided into four groups: 1) terminal QoS, 2) network
`QoS, 3)
`system QoS,
`and 4) availability requirements.
`Thus, QoS parameters must be defined for both terminal
`equipment ( "TE") and network equipment ( "NE") governing the
`
`15
`
`20
`
`25
`
`

`
`W096/23377
`
`PCf/IB96/00ll3
`
`4
`
`is
`System QoS
`the TE.
`communication of data between
`derived from a combination of terminal and network QoS.
`The suggested values for QoS parameters are considered to
`be a practical compromise between required service quality,
`technology and cost. See, Multimedia Communications Forum
`( "MMCF") Working Document "Architecture and Network QoS" I
`(September 1994) and ITU-T
`ARCH/QOS/94-001 1 Rev. 1.7, MMCF 1
`Recommendation !.350 "General Aspects of Quality of Service
`including
`in Digital Networks I
`and Network Performance
`(1993).
`("ISDNs") I
`Integrated Services Digital Networks
`The following Table I summarizes some suggested parameters
`for terminal QoS.
`
`5
`
`10
`
`

`
`W096/ll377
`
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`
`5
`
`Parameter Type
`
`Parameter Value
`
`Audio Frequency
`Range
`
`3.4kHz
`
`Audio Level
`
`-lOdBmO
`
`5
`
`Audio Encoding
`
`G.711 (8-bit
`pulse code
`modulation
`( "PCM"))
`
`Video Resolution
`
`~ 352x288 (SIF)
`
`Video Frame Rate
`
`~ 20 frames per
`second (fps)
`
`10
`
`Voice/Video
`Intramedia(cid:173)
`Intermedia
`Differential
`Delay
`
`< 100
`milliseconds {ms)
`
`Video Encoding
`
`H.261 & Motion
`Picture Experts
`Group ( "MPEG") -1
`
`Parameter
`Explanation
`
`Optimization is
`for voice, and is
`consistent with
`existing Legacy
`voice systems.
`Optimization is
`for voice, and is
`consistent with
`Legacy voice
`systems.
`
`Consistent with
`Legacy voice
`systems.
`
`Minimal
`acceptable size
`for video
`conferencing.
`Minimal
`optimization for
`detection of
`facial expression
`transitions.
`A differential
`delay greater
`than lOOms
`between voice &
`video is
`noticeably
`significant.
`
`H.261 meets WAN
`interoperability,
`MPEG-1 is more
`consistent with
`desktop trends
`and quality
`requirements.
`
`

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`
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`
`Parameter Type
`
`Parameter Value
`
`Intramedia
`Latency (TE)
`
`< lOOms
`
`User Data Rate
`
`~ 64kbps
`
`Data Encoding
`
`HDLC
`encapsulation
`
`Parameter
`Explanation
`
`The delay of the
`TE itself for
`encoding and
`framing purposes.
`
`Minimal
`acceptable data
`bandwidth for
`data sharing
`applications.
`Consistent with
`ISDN Basic Rate
`Instrument
`( "BRI") .
`
`Consistent with
`isochronous
`service bearer
`channels.
`
`5
`
`10
`
`Table I - Terminal QoS Parameters
`
`Network QoS parameter requirements consist of those
`parts of the system that are between two TE endpoints.
`the private
`itself,
`This includes a portion of the TE
`the public network
`and
`required),
`(if
`network
`the
`imposed upon
`the requirements
`Some of
`required) .
`network QoS are a result of the terminal QoS parameters.
`the network QoS
`summarizes
`II
`following Table
`The
`
`(if
`
`requirements.
`
`

`
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`
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`
`7
`
`Parameter
`Value
`
`< SOms
`
`Parameter Type
`
`Intramedia
`Latency (NE)
`
`Parameter Explanation
`
`Intramedia latency is
`the delay between
`source TE transmis-
`sian and destination
`TE reception; i.e.
`the delay of NE.
`
`Network
`Capacity
`
`5
`
`:!: 1,536 kbps G.711 Audio (64
`kbps), MPEG-1 Video
`(1, 344kbps), HDLC
`data (128kbps).
`
`Table II - Network QoS Parameters
`
`The system QoS encompasses the terminal and network
`elements. The particular value critical to the system is
`the intramedia latency. The following Table III summarizes
`this vaiue that is the sum of the terminal and network
`values for the same parameter.
`
`10
`
`Parameter Type
`
`Intramedia
`Latency (System)
`
`Parameter
`Value
`
`< 150ms
`
`Parameter Explanation
`
`Intramedia latency is
`the delay between
`source transmission
`and destination
`reception.
`It
`includes latency
`imposed by the source
`and destination TEs
`as well as the NE.
`These latency values
`might include
`encoding and decoding
`delays, transmission
`delays, and
`adaptation delays.
`
`15
`
`Table III - System QoS Parameters
`
`SUBSTITUTE SHEET (RULE 26)
`
`

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`
`8
`
`The system QoS parameter of Intramedia Latency is the
`Intramedia Latency parameter
`sum of the TE and NE latency.
`value is bounded by voice requirements since latent delay
`the eye.
`than
`is more readily perceived by· the ear
`5 However, the delay itself is'typically a function of video
`time for
`since it is the component requiring the most
`encoding and decoding.
`In
`Availability ("up-time") includes several aspects.
`have very strict
`elements
`network
`the
`particular,
`requirements. These requirements are typical of private
`branch exchanges ("PBXs") and other private network voice
`equipment, but are very atypical of Legacy LANs. Most LANs
`are susceptible to power-losses, single points of failure,
`An interactive multimedia system must
`and errant TE.
`15 closely follow the availability requirements of the legacy
`summarizes
`IV
`following- Table
`The
`systems.
`voice
`Availability QoS parameters.
`
`10
`
`

`
`W096/llJ77
`
`PCTIJB96100l23
`
`9
`
`Parameter '!ype
`
`Parameter Value Parameter
`Explanation
`
`TE Power
`Requirements
`
`NE Power
`Requirements
`
`5
`
`5 watts (W) of
`phantom power
`(48 volts (V) )
`
`This power
`requirement is
`consistent with
`the ISDN BRI
`requirements and
`will allow the
`least common
`denominator of
`voice to function.
`Uninterruptable NE must be UPS
`power supply
`c~pable including
`("UPS")
`private NE.
`
`Single point of
`failure
`
`12 Users
`
`Error Free
`Seconds Ratio
`( "EFS")
`
`10
`
`> 99.9%'
`
`No more than 12
`users should be
`impacted by a
`single point of
`failure.
`
`Meets requirement
`of random bit
`error rate of 10'6 •
`
`Table IV - Availability QoS Parameters
`
`The availability requirements are defined solely
`within the context of the private network. Additional
`availability parameters are discussed in G.821. See also,
`15 MMCF Working Document "Architecture and Network QOS" ,
`ARCH/QOS/94-001, Rev. 1.7, Multimedia Communications Forum,
`Inc., (September 1994) and TR-TSY-000499, Transport Systems
`Generic Requirements (TSGR): Common Requirements, Bellcore
`Technical Reference, Issue 3,
`(December 1989) .
`The second of the fundamental integration issues is
`network services.
`Network services
`include
`transport
`
`20
`
`

`
`W09612J377
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`
`10
`
`services, connection management and feature management.
`Multimedia cormnunication involves the transmission of data
`having more varied characteristics than video, voice or
`the manner in which the
`data in isolation. Therefore,
`5 network transports and manages'the flow of video, voice and
`data is critical to the efficiency, flexibility and overall
`effectiveness of the network.
`three
`into
`Transport services can be categorized
`groups: 1) packet, 2) circuit and 3) cell. The following
`these
`10 Table v summarizes different aspects of each of
`transport services.
`
`Circuit
`
`ISDN, Tl
`
`Cell
`Asynchronous
`Transfer
`Mode
`("ATM")
`
`Packet &
`isochronous
`data
`
`Isochronous
`data (voice,
`video)
`Point-point, Point-point,
`full-duplex,
`full-duplex,
`high-speed
`low-cost
`switching
`switching
`
`Typical
`technology
`
`15 Meqia
`optimization
`
`Transport
`optimization
`
`20
`
`Optimized
`data size
`
`Transport
`Overhead
`
`Packet
`Ethernet®,
`Token Ring®,
`Frame
`Relay®, etc.
`
`Packet data
`
`Multicast,
`shared
`medium
`operations
`
`1500 bytes
`(Ethernet®)
`
`4.2% (64
`bytes - IP)
`
`1 byte
`(voice)
`
`none
`
`48 bytes
`
`(6
`11. 3%'
`bytes -
`AALl)
`
`Switched
`
`Transport
`Methodology
`
`Shared
`
`Switched
`
`

`
`wo 961'1J377
`
`PCI'IIB96/001l3
`
`Packet
`
`Routing
`
`Route
`Methodology
`
`Typical
`Deployment
`
`Widespread. Widespread.
`Deployed as
`Deployed as
`both public
`LAN
`network and
`private NE
`
`11
`
`Circuit
`
`Cell
`
`Signalling
`(circuit
`switching)
`
`Signalling
`(virtual
`circuit
`switching)
`
`very few
`installation
`s.
`Typically
`deployed as
`private
`backbone
`network
`
`5
`
`Table V - Transport Services
`
`Interactive multimedia
`requires
`the usage of an
`isochronous network because of the QoS requirements for
`voice and video . While it is possible to construct a
`packet network with sufficient bandwidth, buffering and
`intelligence to accommodate synchronous traffic it is
`considered to be prohibitively expensive and unnecessary.
`Nevertheless,
`both
`the
`PBX
`LAN,
`and WAN
`
`require
`
`10
`
`interoperability.
`
`At some point it is expected that the entire private
`15 network
`infrastructure will employ ATM.
`This will
`transpire upon the occurrence of several events. First,
`WANs must adapt to support ATM Points-of-Presence ("POPs").
`Second,
`the
`telephone must disappear
`from
`the premise
`(replaced by an ATM audio device). Third, packet-based LAN
`20 TE must become ATM TE.
`Fourth, phantom power must be
`supported
`to
`the ATM TE {for availability purposes).
`Fifth, an 8kHz synchronous clock must be supported and
`
`

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`W096/lJ377
`
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`
`12
`
`Finally, the price of ATM TE
`and
`ISDN,
`
`of Ethernet®,
`
`5
`
`10
`
`managed by all ATM equipment.
`that
`and NE must approach
`isoEthernet® equipment.
`network
`private
`interim
`the
`of
`Regardless
`infrastructure, ATM is the only backbone solution for the
`It is the only scalable switching
`private network.
`isochronous
`architecture that can transport packet and
`data. Furthermore, because it is deployed as a backbone,
`the aforementioned issues do not apply.
`Connection management is the process employed by the
`Because
`private and public network routing functions.
`packet routing is a well established and defined process,
`it is not discussed further. Connection management within
`isochronous network for interactive
`the confines of an
`15 multimedia is a newer technology (albeit with old roots)
`and deserves discussion.
`Signalling for circuit and cell switching is best
`(see, TR-NWT-
`ISDN signalling standards
`defined by the
`000938, Network Transmission Interface and Performance
`Integrated Digital Services
`20 Specification Supporting
`Issue 1,
`(ISDN) , Bell core Technical Reference,
`Network
`(August 1990)), isoEthernet® signalling (see, IEEE Proposed
`Standard B02.9a, "Isochronous services with Carrier Sense
`Multiple Access with Collision Detection (CSMA/CD) Media
`(December 1994)) and ATM
`(MAC) service",
`25 Access Control
`"ATM User-Network Interface
`signalling (see, ATM Forum,
`(September 1993 l and ITU-T
`Specification - Version 3. 0",
`Recommendation Q.293x, "Generic Concepts for the Support of
`(1993)).
`Calls";
`and Multiconnection
`Multipoint
`
`

`
`W0961l3377
`
`PCI'IIB96/00223
`
`13
`
`Historically,
`
`isochronous networks carry the signalling
`channel as an
`isochronous channel.
`Nevertheless,
`the
`signalling function can be showri to be better suited to a
`packet channel.
`A hub/routing· function is the ideal
`location to perform the bridging between an isochronous
`signalling channel and a packet signalling channel. The
`natural packet protocol choice for a signalling channel is
`an Internet Protocol ("IETF IP"). Available on most LAN
`networks, as well as global routing capability, IP greatly
`10 enhances
`the
`signalling
`requirement
`of
`
`5
`
`interactive
`
`multimedia.
`
`by
`
`Feature management consists of those features provided
`the private and public network for
`interactivity
`purposes. The PBX is followed as a model for interactive
`15 multimedia features.
`The following Table VI summarizes
`some of the more common features.
`
`

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`
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`
`14
`
`User Services
`Buzz Station
`Callback
`
`Call Park
`
`Call Pickup
`
`Maintenance
`Automatic Restart
`Connection Detail
`Recording
`
`Default
`Installation
`Class of Service
`
`Hot Configuration
`
`System Services
`Account Codes
`Authorization
`Codes
`Automatic Number Call Forward
`Identification
`Direct Inward
`Dialing ("DID")
`Direct Outward
`10 Dialing ("DOD")
`Hunt Groups
`
`5
`
`Call Waiting
`
`15
`
`Do Not
`Multimedia on
`Disturb/Override
`hold
`Network Numbering Hold/Consultation
`Hold
`Plan
`Number Dial Plan Last Number
`Redial
`Shared Resource Multiple/Shared
`Call Appearances
`Queuing
`Conference
`System Speed
`(multiparty)
`20 Dialing
`Transfer
`Vacant Number
`Intercept
`
`Table VI - Feature Management
`
`25
`
`The third of the fundamental integration issues is
`An interactive multimedia system by
`interoperability.
`interoperability, because a multimedia
`implies
`nature
`network as envisioned is too large and far-flung to employ
`Therefore,
`the equipment of only a single supplier.
`standards must be established that allow equipment from
`To this end,
`30 different suppliers to interact smoothly.
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`interoperability must extend
`to
`transport mechanisms,
`signalling and compression standards.
`There are certain existing communication technologies
`that must be supported and others that are used. A truly
`interoperable
`interactive multimedia
`system
`should
`guarantee that the physical and logical interfaces of each
`component adheres to a standard. Prior to 1992, this would
`have been almost impossible. The present day affords the
`opportunity to evolve the proprietary telephony of the PBX
`10 and the proprietary video of the video conferencing systems
`into standards-based systems in the same manner that the
`data systems evolved from proprietary mainframes to the
`standards-based LAN systems of today. The following Table
`VII summarizes the required standards of interoperability.
`
`15
`
`Transport
`Standards
`
`isoEthernet®
`(IEEE 802. 9a)
`
`ATM
`
`20
`
`ISDN
`
`Signalling
`Standards
`
`ISDN NI-2
`
`QSIG
`
`Q.2931
`
`H.320
`(Audiovisual)
`
`Compression
`Standards
`
`G. 711, G.722
`(Audio)
`
`H.221 (Video)
`
`MPEG-1 (Video)
`
`Table VII - Interoperability Standards
`
`In
`required
`addition
`standards
`to
`the
`for
`communications,
`there are other standards relating to
`application programming interfaces for terminal and server
`25 control. These include Microsoft® Telephony Application
`
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`( "TAPI®n) ,
`
`Novell
`
`TSAPI®,and
`
`Interface
`Programming
`Microsoft® ODBC®.
`Having now set the stage with a discussion of general
`issues concerning multimedia systems, more specific design
`issues may now be discussed.' 'The specific design issue of
`concern is provision of power to guarantee TE availability.
`the
`for
`provides
`802. 9a
`standard
`IEEE draft
`integration of video, voice and data services to a desktop
`computer system. A needed step in the evolution of this
`integration is to provide for a level of.service equal to
`or greater than that currently available from LAN, PBX and
`WAN systems.
`In the case of voice services, i.e. telephony, users
`In the
`have come to expect service under all conditions.
`PBX realm, this is commonly referred to as "dialtone is an
`Users expect basic voice service
`inalienable right."
`regardless of the state of the desktop computer system,
`time of day and other external
`building power, weather,
`factors.
`This principal is in concert with the above-mentioned
`requirement that power must be supported to the ATM TE for
`availability purposes to establish ATM as the foundation
`for the private network infrastructure. The TE thus must
`support at least voice in case of power or device failure
`25 of the client.
`Power for the TE can be supplied in one of three ways.
`First, a local (in the office) power supply can supply
`power to the TE, much in the same way an uninterruptable
`to a . personal
`to supply power
`power supply functions
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`computer ("PC") in case of power failure. This is local
`powering.
`Second, power may be routed through the same
`cable employed to carry data through the network. This is
`phantom powering and is employed
`in current
`telephone
`systems. Third, power may be routed through a separate,
`dedicated power cable. Since LANs often operate with a two
`twisted-pair data bus, this method of delivering power is
`often called third pair powering.
`Local powering,
`though possible,
`is
`relatively
`10 expensive, especially in the case of large multimedia
`installations, because a dedicated power supply providing
`power back-up must be purchased and coupled to the TE.
`Phantom powering has the advantage of not requiring
`the installation of a dedicated power cable. However,
`15 since power is carried on the data bus a careful phantom
`power scheme must be implemented to avoid problems that may
`arise due to interactions between the power and the data,
`causing instability and imbalance on the bus and thereby
`reducing reliability.
`Third pair powering has the advantage of separating
`the power
`from
`the data,
`thereby avoiding potentially
`harmful
`interactions.
`This also preserves existing
`standard bus interface circuitry. However,
`third pair
`powering requires a dedicated power cable, increasing the
`25 cost of new installations and existing installations where
`a dedicated power cable is not already in place.
`It is desirable to provide options for both phantom
`and third pair powering in the environment of a local area
`network without significantly altering the topology of the
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`network. Accordingly, what ,is needed in the art are a
`power subsystem and method for a multimedia subsystem that
`provide a central power source and distribution of the
`power to equipment comprising.the system within the context
`5 of LAN or isochronous LAN transport mediums.
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`SUMMARY OF THE INVENTION
`
`To address the above-discussed deficiencies of the
`prior art, it is a primary object of the present invention
`to provide power subsystems for' providing either phantom or
`
`5
`
`local area
`third pair power to equipment coupled to. a
`network,
`including, but not limited to, Ethernet®, Token
`Ring®, ATM
`and
`isoEthernet®.
`The
`subsystems allow
`equipment coupled to the network to be available even when
`the network is not operating due to an absence of local
`10 power.
`
`It is a further primary object of the present
`invention to remain as compatible as possible with existing
`standards for video, voice and data communication.
`In the attainment of the above primary objects, the
`present invention provides a power subsystem and method for
`15 providing phantom power and third pair power via a computer
`network backbone,
`the bus
`including first and second
`conductors.
`In a first aspect, the present invention provides a
`phantom power subsystem comprising:
`( 1) a power supply
`20 having a positive output and a negative output, the power
`supply adapted
`to provide power via
`the positive and
`negative outputs and
`(2) first and second transformers,
`each of the first and second transformers having a winding,
`each of the windings having a pair of end taps and a center
`tap, the first conductor coupled to the end taps of the
`allow data
`first
`transformer
`to
`winding
`the
`of
`communication therebetween, the second conductor coupled to
`the end taps of the winding of the second transformer to
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`the positive and
`allow data communication therebetween,
`negative outputs of the power supply coupled to the center
`taps of the windings of the first and second transformers,
`respectively, to allow the power supply to transmit the
`5 power, via the first and secon.d transformers and the first
`and second conductors, to equipment couplable to the first
`the first and
`In one embodiment,
`and second conductors.
`second conductors are twisted-pair conductors, although
`untwisted-pair, coaxial and other conductors are within the
`scope of the present invention.
`in this first aspect,
`the present invention,
`Thus,
`provides a power supply, center-tap transformer combination
`allowing power to be introduced into the conductors and
`the concept of
`Thus,
`throughout the computer network.
`15 phantom power has been extended significantly to operate
`with data-bearing LAN buses. At this point, it should be
`used
`be
`"cable" may
`and
`"conductor"
`that
`noted
`interchangeably.
`It is also apparent that the above first aspect of the
`20 present invention provides a phantom powering subsystem
`the
`suitable for powering a multimedia system meeting
`general design criteria set forth in the Background of the
`Invention.
`In a preferred embodiment of the first aspect of the
`the subsystem further comprises third
`25 present invention,
`the third and fourth
`transformers, each of
`and fourth
`transformers having a winding, each of the windings having
`a pair of end taps and a center tap, the first conductor
`third
`the
`the winding of
`taps of
`coupled to the end
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`transformer to allow data communication therebetween, the
`
`second conductor coupled to the end taps of the winding of
`
`the
`
`fourth
`
`transformer
`
`to allow data
`
`communication
`
`therebetween, the positive and negative inputs of equipment
`
`5 coupled to the center taps of the windings of the third and
`
`fourth
`
`transformers,
`
`respectively,
`
`to allow
`
`the power
`
`supply to transmit the power, via the first and second
`
`transformers, the first and second conductors and the third
`
`and fourth transformers, to the equipment.
`
`10
`
`The third and fourth transformers allow the equipment
`In an overall LAN, many
`
`to draw power from the conductors.
`
`pieces of equipment, each with its own third and fourth
`
`transformers, can take power as well as data from the bus.
`
`Thus,
`
`telephone instruments coupled to the equipment can
`
`15
`
`remain powered even when associated devices are not or in
`
`the event of a power failure.
`
`In a preferred embodiment of the first aspect of the
`
`present invention, the bus comprises a 10Base-T bus. Those
`
`of skill in the art will recognize, however,
`
`that the
`
`20 present invention is also compatible with Ethernet®, Token
`
`Ring®, ATM and isoEthernet® standards.
`
`A lOBase-T bus conventionally comprises two twisted(cid:173)
`
`pair conductors, each used for unidirectional transmission
`
`of data.
`
`Thus,
`
`in this embodiment, one of the twisted
`
`25 pairs is employed for transmitting data from equipment,
`
`while the other of the twisted-pairs is used for receiving
`
`data into the equipment. The present invention preferably
`
`employs each of the twisted-pair conductors as a rail by
`
`which to deliver DC power to the equipment.
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`The windings of the first and second transformers may
`two center taps and may employ a balance circuit
`have
`coupling the two center taps of each of the windings of the
`first and second transformers to the positive and negative
`In a manner to be described more
`5 outputs, respectively.
`particularly, the balance circuit is designed to correct
`the
`in
`that may be present
`imbalances
`any current
`conductors due to varying impedances therein.
`The subsystem may further comprise first and second
`10 balance circuits coupling the positive and negative outputs
`to the center taps of the windings of the first and second
`two balance circuits may
`transformers, respectively. Thus,
`be employed to balance the two conductors against each
`other. Of course, those of skill in the art will recognize
`that the balance circuits may be deleted at the risk of
`impairing signal quality.
`In a preferred embodiment of the first aspect of the
`second
`and
`first
`the
`each of
`invention,
`present
`the second windings
`transformers has a second winding,
`coupled to respective filter circuits.
`The first and second transformers therefore act as
`isolation transformers, isolating the DC bias of the power
`subsystem from data inputs on the equipment. Accordingly,
`the second windings are coupled to filters to provide
`further conditioning of the data signals before they are
`introduced into the equipment.
`In a preferred embodiment of the first aspect of the
`subsystem further comprises a
`the
`invention,
`present
`protective device coupled to the power supply to prevent
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`5
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`power exceeding a desired amount from passing through the
`protective device.
`The protective device is more preferably a resettable
`device, such as a thermistor or polyfuse, designed mutually
`to protect the power supply and the bus from overcurrents
`that may damage either. Of course, such protective device
`is desirab