WORLD INTELI..ECI'UAL_ PROPERTY ORGANIZATION
`lntemattonal Bureau
`
`INTERNAT'IONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(51) International Patent Classification 5 =
`H04L 12fl0, H04Q 11/04, I-I04M 19/08
`
`(11) International Publication Number:
`,
`(43) International Publication Date:
`
`WO 96123377
`
`I August 1996 (Ol.08.96)
`
`(21) International Application Number:
`
`(22) International Filing Date:
`
`26 January 1996 (26.0l.96)
`
`(30) Priority Data:
`08/379,365
`
`27 January 1995 (2701.95)
`
`US
`
`INCORPORATED [US/US]; 5057
`INTECOM,
`(71) Applicant:
`Keller Springs Road, Dallas, TX 75248 (US).
`
`SE, SG, SI, SK, TI, TM,
`UG), Eurasian patent (AZ,
`patent (KE, LS, MW, 8
`BY, KG, KZ, RU, TI, TM), European patent (AT, BE, CH,
`DE, DK, ES, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE),
`OAPI patent (BF, BJ, CF. CG, CI, CM. GA, GN, ML, MR,
`NE, SN, TD, TG).
`
`(72) Inventors: HUNTER, Richard, K.; Apartment 804, 4815 Published
`Westgrove Road, Dallas, TX 75248 (US). PLA'I'I‘, Richard,
`With international search report.
`B.; llll Ashby Drive, Allen, TX 75002 (US).
`Before the expiration of the time limit for amending the
`claims and to be republished in the event of the receipt of
`amendments.
`
`(74) Agent: HITI‘, David, H.; Hitt Chwang & Gaines, P.C., Suite
`225, 275 West Campbell Road, Richardson, TX 75080 (US).
`
`(54) Title: 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 transfonners, each of the first and
`second transfonners 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 transfonner 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 transfonners. 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.
`
`D-Link-1008
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`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international
`applications under the PCI'.
`
`AM
`AT
`AU
`BB
`BE
`BF
`BG
`31
`BR
`BY
`CA
`CF
`
`Armenia
`Austria
`Australia
`Barbados
`Belgium
`Buriina Faro
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`Cote d'lvoire
`Cameroon
`China
`Czechoalovvakia
`Czech Republic
`
`United Kingdom
`Georgia
`Guinea
`Greece
`Hungary
`Ireland
`My
`Japan
`Kenya
`Kyrgystan
`Democratic People's Republic
`of Korea
`Republic of Korea
`Kazakhstan
`Liechtenstein
`Sri Lanka
`Liberia
`Lithuania
`Luxembourg
`Latvia
`Monaco
`Republic of Moldova
`
`MW
`MX
`NE
`N1.
`NO
`NZ
`PL
`PT
`RO
`RU
`SD
`SE
`SG
`SI
`SK
`SN
`SZ
`TD
`TG
`T1
`1'!‘
`UA
`UG
`US
`UZ
`VN
`
`Malawi
`Muico
`Niger
`Netherlands
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`Sweden
`Singapore
`Slovenia
`Slovakia
`Senegal
`Swaziland
`Chad
`Togo
`Tajikistan
`‘lhnirlad and Tobago
`Ukraine
`Uganda
`United States of America
`Uzbekistan
`Vie! Nam
`
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`wo 96l23377
`
`PCT/lB96I00223
`
`MULTIMEDIA SYSTEM HAVING CENTRAL POWER SOURCE
`
`AND DISTRIBUTION SUBSYSTEM
`
`TECHNICAL FIELD OF THE INVENTION
`
`The present
`
`invention is directed,
`
`in general,
`
`to
`
`multimedia systems
`
`and, more specifically,
`
`to a power
`
`subsystem for
`
`a multimedia subsystem and a method of
`
`providing phantom and third pair power
`
`therefor,
`
`the
`
`subsystem providing a central power source and distribution
`
`of power to equipment comprising the system.
`
`BACKGROUND OF THE INVENTION
`
`Currently, "Information superhighway" and "multimedia"
`
`are probably the most often spoken
`
`and
`
`least often
`
`understood
`
`aspects
`
`of
`
`a
`
`coming
`
`revolution
`
`in
`
`data
`
`communication. Although issues specific to an information
`
`superhighway
`
`are
`
`beyond
`
`the
`
`scope
`
`of
`
`the
`
`present
`
`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
`
`coordinating data pertaining to visual
`
`information, aural
`
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`wo 96123377
`
`PCTIIB96l00223
`
`2
`
`information and other information. Visual
`
`information is
`
`generally divided into still picture or graphics and full
`
`motion video or animation categories.
`
`In the vernacular of
`
`those involved in multimedia,
`
`such visual
`
`information is
`
`generically referred to as "video." Aural
`
`information is
`
`generally divided into speech and non-speech categories and
`
`is
`
`generically referred to
`
`as
`
`"voice."
`
`“Other
`
`information“ is directed primarily to computer data, often
`
`organized in files and records,
`
`and perhaps constituting
`
`textual
`
`and graphical data.
`
`Such
`
`computer data are
`
`generally referred to as "data."
`
`To date, multimedia has,
`
`for
`
`the most part, been
`
`limited to stand-alone computer systems or computer systems
`
`linked together in a local area network ("LAN"). While
`
`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
`
`systems are developed,
`
`standardized and installed that
`
`permit
`
`truly interactive multimedia.
`
`Such multimedia
`
`systems will allow long distance communication of useful
`
`quantities of coordinated voice, video and data, providing,
`
`in effect,
`
`a multimedia
`
`extension to the voice-only
`
`services of the ubiquitous telephone network.
`
`Defining the structure and operation of an interactive
`
`multimedia
`
`system is
`
`a critical
`
`first
`
`step in the
`
`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
`
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`WO 96/23377
`
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`
`3
`
`a whole
`
`and
`
`some generally agreed-upon
`
`answers
`
`and
`
`specifications.
`
`Interactive multimedia may be
`
`thought of
`
`as
`
`an
`
`electronic approximation of
`
`the paradigm of
`
`interactive
`
`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
`
`nmltimedia retrieval systems.
`
`some of
`
`the more obvious
`
`examples of those requirements and services include latency
`
`(transmission delay),
`
`conferencing,
`
`availability ("up-
`
`time") and WAN interoperability.
`
`The evolution of existing private 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 Q08, 2) network
`
`Q08,
`
`3)
`
`system QoS,
`
`and 4) availability requirements.
`
`Thus,
`
`Qos parameters must be defined for both terminal
`
`equipment
`
`("TE") and network equipment
`
`("NE") governing the
`
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`
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`
`4
`
`communication of data between the TE.
`
`Systeum Qos
`
`is
`
`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",
`
`ARCH/QOS/94-O01, Rev. 1.7, MMCF,
`
`(September 1994) and ITU-T
`
`Recomendation 1.350 "General Aspects of Quality of Service
`
`and Network Performance in Digital Networks,
`
`including
`
`Integrated. Services Digital Networks
`
`("ISDNS"),
`
`(1993).
`
`The following Table I sumarizes some suggested parameters
`
`for terminal Qos.
`
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`
`5
`
`Parameter Type
`
`Parameter Value
`
`Parameter
`
`Audio Frequency
`Range
`
`3.4kHz
`
`Audio Level
`
`-10dBmO
`
`Explanation
`
`Optimization is
`for voice, and is
`consistent with
`
`existing Legacy
`voice systems.
`
`Optimization is
`for voice, and is
`consistent with
`
`Legacy voice
`systems.
`
`Audio Encoding
`
`G.711 (8—bit
`
`Consistent with
`
`pulse code
`modulation
`
`(llPCMll))
`
`Legacy voice
`systems.
`
`Video Resolution
`
`2 352x288 (SIF)
`
`Minimal
`
`Video Frame Rate
`
`2 20 frames per
`second (fps)
`
`Voice/Video
`Intramedia-
`
`Intermedia
`
`Differential
`
`Delay
`
`< 100
`
`milliseconds
`
`(ms)
`
`acceptable size
`for video
`
`conferencing.
`
`Minimal
`
`optimization for
`detection of
`
`facial expression
`transitions.
`
`A differential
`
`delay greater
`than 100ms
`
`between voice &
`video is
`
`noticeably
`significant.
`
`Video Encoding
`
`H.261 & Motion
`
`H.261 meets WAN
`
`Picture Experts
`Group ("MPEG")—l
`
`interoperability,
`MPEG-1 is more
`
`consistent with
`
`desktop trends
`
`and quality
`requirements.
`
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`Parameter Type
`
`Parameter Value
`
`Intramedia
`Latency (TE)
`
`< looms
`
`Parameter
`Explanation
`
`The delay of the
`TE itself for
`encoding and
`
`framing purposes.
`
`User Data Rate
`
`2 64kbps
`
`Minimal
`
`acceptable data
`bandwidth for
`
`data sharing
`
`applications.
`Consistent with
`
`ISDN Basic Rate
`Instrument
`
`("BRI").
`
`Consistent with
`
`isochronous
`service bearer
`
`channels.
`
`Data Encoding
`
`HDLC
`
`encapsulation
`
`Table I
`
`- Terminal QoS Parameters
`
`Network Qos parameter requirements consist of
`
`those
`
`parts of
`
`the system that are between two TE endpoints.
`
`This
`
`includes a portion of
`
`the TE itself,
`
`the private
`
`network
`
`(if
`
`required),
`
`and
`
`the
`
`public
`
`network
`
`(if
`
`required).
`
`some of
`
`the requirements
`
`imposed upon the
`
`network Qos are a result of the terminal Qos parameters.
`
`The
`
`following Table
`
`II
`
`summarizes
`
`the
`
`network Qos
`
`requirements.
`
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`Intramedia
`Latency (NB)
`
`Value
`
`< 50ms
`
`Network
`Capacity
`
`2 1,536 kbps
`
`Intramedia latency is
`the delay between
`source TE transmis-
`
`sion and destination
`
`TE reception; i.e.
`
`the delay of NE.
`
`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 value that
`is the sum of
`the terminal and network
`values for the same parameter.
`
`Intramedia
`Latency (System)
`
`Value
`
`< 1SOms
`
`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.
`
`Table III — System Qos Parameters
`
`SUBSTITUTE SHEET (RULE 26)
`
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`8
`
`The system QoS parameter of Intramedia Latency is the
`
`sum of the TE and NE latency.
`
`Intramedia Latency parameter
`
`value is bounded by voice requirements since latent delay
`
`is more
`
`readily perceived by
`
`the ear
`
`than the
`
`eye.
`
`However,
`
`the delay itself is typically a function of video
`
`since it
`
`is the component
`
`requiring the most
`
`time for
`
`encoding and decoding.
`
`Availability ("up-time")
`
`includes several aspects.
`
`In
`
`particular,
`
`the
`
`network
`
`elements
`
`have
`
`very
`
`strict
`
`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,
`
`and errant TE.
`
`An
`
`interactive multimedia systenl must
`
`closely follow the availability requirements of the legacy
`
`voice
`
`systems.
`
`The
`
`following Table
`
`IV summarizes
`
`Availability Qos parameters.
`
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`
`Parameter Type
`
`Parameter Value
`
`TE Power
`Requirements
`
`5 watts (W) of
`phantom power
`(48 volts (V))
`
`_
`Parameter
`Explanation
`
`This power
`requirement is
`consistent with
`the ISDN BRI
`
`requirements and
`will allow the
`least comon
`
`denominator of
`
`voice to function.
`
`NE Power
`Requirements
`
`Uninterruptable
`power supply
`("UPS")
`
`NE must be UPS
`capable including
`private NE.
`
`Single point of
`failure
`
`12 Users
`
`Error Free
`Seconds Ratio
`("EFS")
`
`No more than 12
`users should be
`
`impacted by a
`single point of
`failure.
`
`Meets requirement
`of random bit
`error rate of 10*.
`
`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,
`
`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
`
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`10
`
`services,
`
`connection management and feature nanagement.
`
`Multimedia communication involves the transmission of data
`
`having more varied characteristics than video, voice or
`
`data in isolation.
`
`Therefore,
`
`the manner
`
`in which the
`
`network transports and manages the flow of video, voice and
`
`data is critical to the efficiency, flexibility and overall
`
`effectiveness of the network.
`
`Transport
`
`services
`
`can be categorized into three
`
`groups: 1) packet, 2) circuit and 3) cell.
`
`The following
`
`Table V summarizes different aspects of each of
`
`these
`
`transport services.
`
`— T
`
`ypical
`technology
`
`Ethernet@,
`Token Ring®,
`Frame
`
`ISDN, T1
`
`Asynchronous
`Transfer
`Mode
`("ATM")
`
`Re1ay®, etc.
`
`Media
`
`Packet data
`
`Isochronous
`
`Packet &
`
`optimization
`
`data (voice,
`video)
`
`isochronous
`data
`
`Transport
`
`Multicast,
`
`Point-point,
`
`Point-point,
`
`optimization
`
`shared
`
`full-duplex,
`
`full-duplex,
`
`medium
`
`1ow—cost
`
`high—speed
`
`operations
`
`switching
`
`switching
`
`Optimized
`data size
`
`1500 bytes
`(Ethernet®)
`
`1 byte
`(voice)
`
`Transport
`Overhead
`
`4.2% (64
`bytes -
`
`IP)
`
`48 bytes
`
`11.3% (6
`bytes -
`AAL1)
`
`Transport
`
`Shared
`
`Switched
`
`Switched
`
`Methodology
`
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`Route
`Methodology
`
`Signalling
`(circuit
`
`Signalling
`(virtual
`
`switching)
`
`circuit
`
`Typical
`Deployment
`
`Widespread. Widespread.
`Deployed as
`Deployed as
`LAN
`both public
`
`network and
`private NE
`
`switching)
`
`Very few
`installation
`s.
`
`Typically
`deployed as
`private
`backbone
`network
`
`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
`
`LAN,
`
`PBX
`
`and
`
`WAN
`
`require
`
`interoperability.
`
`At some point it is expected that the entire private
`
`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
`
`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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`12
`
`managed by all ATM equipment. Finally,
`
`the price of ATM TE
`
`and
`
`NE must
`
`approach
`
`that
`
`of Ethernet@,
`
`ISDN,
`
`and
`
`isoEthernet® equipment.
`
`Regardless
`
`of
`
`the
`
`interim private
`
`network
`
`infrastructure, ATM is the only backbone solution for the
`
`private network.
`
`It
`
`is
`
`the only scalable switching
`
`architecture that
`
`can transport packet
`
`and isochronous
`
`data.
`
`Furthermore, because it is deployed as a backbone,
`
`the aforementioned issues do not apply.
`
`Connection management is the process employed by the
`
`private and public network routing functions.
`
`Because
`
`packet routing is a well established and defined process,
`
`it is not discussed further. Connection management within
`
`the confines of an isochronous network for
`
`interactive
`
`multimedia is a newer
`
`technology (albeit with old roots)
`
`and deserves discussion.
`
`Signalling for circuit and cell
`
`switching is best
`
`defined by the ISDN signalling standards
`
`(see,
`
`TR—NWT-
`
`000938, Network Transmission Interface and Performance
`
`Specification
`
`Supporting
`
`Integrated Digital
`
`Services
`
`Network
`
`(ISDN), Bellcore Technical Reference,
`
`Issue 1,
`
`(August 1990)),
`
`isoEthernet® signalling (see,
`
`IEEE Proposed
`
`Standard 802.9a, "Isochronous services with Carrier Sense
`
`Multiple Access with Collision Detection (CSMA/CD) Media
`
`Access Control
`
`(MAC)
`
`service",
`
`(December 1994))
`
`and ATM
`
`signalling (see, ATM Forum,
`
`"ATM User-Network Interface
`
`Specification - Version 3.0",
`
`(September 1993)
`
`and ITU—T
`
`Recommendation Q.293x, “Generic Concepts for the Support of
`
`Multipoint
`
`and Multiconnection
`
`Calls";
`
`(1993)).
`
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`Historically,
`
`isochronous networks carry the signalling
`
`channel as
`
`an isochronous channel.
`
`Nevertheless,
`
`the
`
`signalling function can be shown 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
`
`enhances
`
`the
`
`signalling
`
`requirement
`
`of
`
`interactive
`
`multimedia.
`
`Feature management consists of those features provided
`
`by
`
`the private and public network for
`
`interactivity
`
`purposes.
`
`The PBX is followed as a model for interactive
`
`multimedia features.
`
`The following Table VI
`
`summarizes
`
`some of the more common features.
`
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`System Services
`
`User Services
`
`Maintenance
`
`Account Codes
`
`Buzz Station
`
`Automatic Restart
`
`Authorization
`
`Callback
`
`Connection Detail
`
`Codes
`
`Recording
`
`Automatic Number
`
`Call Forward
`
`Default
`
`Identification
`
`Installation
`
`Direct Inward
`
`Call Park
`
`Class of Service
`
`Dialing ("DID")
`
`Direct Outward
`
`Call Pickup
`
`Hot Configuration
`
`Dialing ("DOD")
`
`Hunt Groups
`
`Call Waiting
`
`Multimedia on
`
`Do Not
`
`hold
`
`Disturb/Override
`
`Network Numbering Hold/Consultation
`Plan
`Hold
`
`Number Dial Plan
`
`Last Number
`Redial
`
`Shared Resource
`
`Multiple/Shared
`
`Queuing
`
`Call Appearances
`
`System Speed
`Dialing
`
`Conference
`(multiparty)
`
`Vacant Number
`
`Transfer
`
`Intercept
`
`Table VI
`
`- Feature Management
`
`The third of
`
`the fundamental
`
`integration issues is
`
`25
`
`interoperability.
`
`An
`
`interactive multimedia systenu by
`
`nature
`
`implies
`
`interoperability,
`
`because
`
`a multimedia
`
`network as envisioned is too large and far-flung to employ
`
`the equipment of only a
`
`single supplier.
`
`Therefore,
`
`standards must be established that allow equipment
`
`from
`
`30 different suppliers to interact smoothly.
`
`To this end,
`
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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
`
`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 sumarizes the required standards of interoperability.
`
`Transport
`Standards
`
`isoEthernet®
`(IEEE 802.9a)
`
`Signalling
`Standards
`
`ISDN NI-2
`
`osm
`
`H.320
`
`(Audiovisual)
`
`Compression
`Standards
`
`(3.722
`
`G.7ll,
`(Audio)
`<vmeo>
`wee»
`
`Table VII — Interoperability Standards
`
`In
`
`addition
`
`to
`
`the
`
`standards
`
`required
`
`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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`Programming
`
`Interface
`
`("TAPI@"),
`
`Novell
`
`TSAPI@,and
`
`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.
`
`IEEE
`
`draft
`
`standard
`
`802.9a
`
`provides
`
`for
`
`the
`
`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
`
`have come to expect service under all conditions.
`
`In the
`
`PBX realm,
`
`this is comonly referred to as "dialtone is an
`
`inalienable right."
`
`Users expect basic voice service
`
`regardless of
`
`the state of
`
`the desktop computer system,
`
`building power, weather,
`
`time of day and other external
`
`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
`
`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 TB, much in the same way an uninterruptable
`
`power
`
`supply functions
`
`to supply power
`
`to a personal
`
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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
`
`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,
`
`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
`
`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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`
`SUMARY 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
`
`third pair power
`
`to equipment coupled to a local area
`
`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
`
`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
`
`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
`
`phantmn power
`
`subsystem comprising:
`
`(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
`
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`
`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.
`
`In one embodiment,
`
`the first and
`
`second conductors are twisted-pair conductors,
`
`although
`
`untwisted-pair, coaxial and other conductors are within the
`
`scope of the present invention.
`
`Thus,
`
`the present
`
`invention,
`
`in this first aspect,
`
`provides a power supply, center-tap transformer combination
`
`allowing power
`
`to be introduced into the conductors and
`
`throughout
`
`the computer network.
`
`Thus,
`
`the concept of
`
`phantom power has been extended significantly to operate
`
`with data—bearing LAN buses. At this point,
`
`it should be
`
`noted
`
`that
`
`"conductor"
`
`and
`
`"cable"
`
`may
`
`be
`
`used
`
`interchangeably.
`
`It is also apparent that the above first aspect of the
`
`present
`
`invention provides a phantom powering subsystem
`
`suitable for powering a multimedia systen1 meeting the
`
`general design criteria set forth in the Background of the
`
`Invention.
`
`In a preferred embodiment of the first aspect of the
`
`present
`
`invention,
`
`the subsystem further comprises third
`
`and fourth.
`
`transformers,
`
`each of
`
`the third and fourth
`
`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 third
`
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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
`
`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.
`
`The third and fourth transformers allow the equipment
`
`to draw power from the conductors.
`
`In an overall LAN, many
`
`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
`
`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 1OBase—T bus. Those
`
`of skill
`
`in the art will
`
`recognize, however,
`
`that
`
`the
`
`present invention is also compatible with Ethernet®, Token
`
`Ring®, ATM and isoEthernet® standards.
`
`A 10Base—T bus conventionally comprises two twisted-
`
`pair conductors, each used for unidirectional transmission
`
`of data.
`
`Thus,
`
`in this embodiment,
`
`one of
`
`the twisted
`
`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
`
`have two center
`
`taps and may employ a balance circuit
`
`coupling the two center taps of each of the windings of the
`
`first and second transformers to the positive and negative
`
`outputs,
`
`respectively.
`
`In a manner to be described more
`
`particularly,
`
`the balance circuit
`
`is designed to correct
`
`any
`
`current
`
`imbalances
`
`that may
`
`be present
`
`in the
`
`conductors due to varying impedances therein.
`
`The subsystem may further comprise first and second
`
`balance circuits coupling the positive and negative outputs
`
`to the center taps of the windings of the first and second
`
`transformers, respectively. Thus,
`
`two balance circuits may
`
`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
`
`present
`
`invention,
`
`each
`
`of
`
`the
`
`first
`
`and
`
`second
`
`transformers has a
`
`second winding,
`
`the second windings
`
`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
`
`present
`
`invention,
`
`the
`
`subsystem further
`
`comprises
`
`a
`
`protective device coupled to the power supply to prevent
`
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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 desirable, but not necessary to the present invention.
`
`In a preferred embodiment of the first aspect of the
`
`present invention,
`
`the power is supplied at about 48V. As
`
`previously mentioned,
`
`this power requirement is consistent
`
`with the ISDN BRI
`
`requirements and will allow the least
`
`common denominator of voice to function.
`
`In a preferred embodiment of the first aspect of the
`
`present invention,
`
`the first and second transformers have
`
`a mutual
`
`inductance of
`
`about
`
`350 microhenrys
`
`(pHy).
`
`Transformers of such size are a standard size for a 10Base—
`
`T LAN system.
`
`In a preferred embodiment of the first aspect of the
`
`present invention,
`
`the equipment is an Integrated Services
`
`Terminal Equipment
`
`(“ISTE") device.
`
`Such equipment
`
`is
`
`compatible with ISDN standards. This is in ac