CA2195941A1 - Multi-nodal digital telephone distribution system - Google Patents

Multi-nodal digital telephone distribution system

Info

Publication number
CA2195941A1
CA2195941A1 CA 2195941 CA2195941A CA2195941A1 CA 2195941 A1 CA2195941 A1 CA 2195941A1 CA 2195941 CA2195941 CA 2195941 CA 2195941 A CA2195941 A CA 2195941A CA 2195941 A1 CA2195941 A1 CA 2195941A1
Authority
CA
Canada
Prior art keywords
telephone
telephony
channel
data
control units
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA 2195941
Other languages
French (fr)
Inventor
Fariborz Tavakkolian
Cameron Scott Elliott
Robert K. Lee
Xia Hao Xing
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Claircom Communications Group Inc
Original Assignee
Fariborz Tavakkolian
Cameron Scott Elliott
Robert K. Lee
Xia Hao Xing
Claircom Communications Group, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US28078294A priority Critical
Priority to US280,782 priority
Priority to US37073295A priority
Priority to US370,732 priority
Application filed by Fariborz Tavakkolian, Cameron Scott Elliott, Robert K. Lee, Xia Hao Xing, Claircom Communications Group, Inc. filed Critical Fariborz Tavakkolian
Publication of CA2195941A1 publication Critical patent/CA2195941A1/en
Application status is Abandoned legal-status Critical

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q11/00Selecting arrangements for multiplex systems
    • H04Q11/04Selecting arrangements for multiplex systems for time-division multiplexing
    • H04Q11/0428Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/14Relay systems
    • H04B7/15Active relay systems
    • H04B7/185Space-based or airborne stations; Stations for satellite systems
    • H04B7/18502Airborne stations
    • H04B7/18506Communications with or from aircraft, i.e. aeronautical mobile service
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M9/00Interconnection arrangements not involving centralised switching
    • H04M9/02Interconnection arrangements not involving centralised switching involving a common line for all parties
    • H04M9/022Multiplex systems
    • H04M9/025Time division multiplex systems, e.g. loop systems
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q3/00Selecting arrangements
    • H04Q3/58Arrangements providing connection between main exchange and sub-exchange or satellite
    • H04Q3/62Arrangements providing connection between main exchange and sub-exchange or satellite for connecting to private branch exchanges
    • H04Q3/625Arrangements in the private branch exchange
    • H04Q3/627Details
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q2213/00Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13034A/D conversion, code compression/expansion
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q2213/00Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/1308Power supply
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q2213/00Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13141Hunting for free outlet, circuit or channel
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q2213/00Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13176Common channel signaling, CCS7
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q2213/00Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13204Protocols
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q2213/00Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13205Primary rate access, PRI
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q2213/00Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13209ISDN
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q2213/00Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/1322PBX
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q2213/00Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13333Earth satellites

Abstract

A Cabin Distribution System (CDS) provides the necessary interfaces between each of the telephone units used by the passengers on the airplane and a Cabin Telephony Unit (CTU). The CTU is an intelligent telephony switch that controls and routes telephone calls between the passengers and a plurality of communication networks. A primary rate interface such as a CEPT E1 interface is used to connect the plurality of telephone units to the CTU in a loop-based configuration. The E1 interface provides thirty-two communication channels.
Preferably, a link access protocol over the D-Channel is utilized to control the communications on the E1 interface. Utilizing the LAP-D protocol, of the thirty-two channels available on the E1 interface, a first channel is used for framing the communication messages, and a sixteenth channel, referred to as the D-Channel, is utilized as the data communication channel. Advantageously, the remaining thirty channels, which are referred to as B-Channels, are available to connect telephone calls. Data information transferred on the D-Channel is interrupted by each telephony group for a delay of sixteen frames to determine if the data is intended for the group. Voice information that is transmitted along the B-Channels is only interrupted for one frame by each group to determine if the data is intended for the group. By preventing the groups of telephones from interrupting the transmissions on the B-Channel for an extended length of time, unnecessary and unwanted delays in the voice communication are eliminated.

Description

1 ' , . ' . ~
~ W096/03846 2195941 r~-~o~

MULTI-NODAL DIGITAL TELEPl~ONE DISTRIBUT10N SYSTEM
n~k~uulld of the Invention The present invention relates generally to the field of digital telephone systems.
It is desirable to implement a telephone d~ ;"" system which reduces the number and length of the wires required to cormect a multitude of telephone units to a telephony switching device, such as a Private Automatic Branch Exchange (PABX).
Traditionally, a "star" topology has been used with a PABX at the center with radial ~,--,. ~ I;....i to each telephone unit. However, the "star" topology is not practical for 10 all situations, because of the number and length of wires that are required.
Further, in order to enable a ~ ipli~ y of telephone units to ~ with a central telephony switching device, and vice versa, a ~ protocol which enables point to multi-point ~ must be selected. Common n~lwulki.lg protocols of the prior art, such as Ethernet and Token Ring protocols, enable point to multi-point ~ but are optimized for data l ~ . and not for voice delivery. These data i networks are U,,,l ~.. ' ,:. ;. in their ;.. r.. ~.;
delivery rates. The ~ ' quality of the I rates of these types of networks is not commonly a problem in data 1.~ systems, because it is not critical to the data receiver that the data be received at a specific instant in time.
However, these variations in delivery rate are detrimental to voice ~ . ." because they result in l..,.L rt l~ delays in the ~:u~L;ull.
Therefore, it would be desirable to provide a telephone .l;~l. il .u; ;.... system which connects a nurnber of telephone units to a central telephone control unit and does not suffer from unwanted delays in the llr - ~ of the voice ;. r.. ,-~;, . through the system.

Summarv of the Invention A multi-nodal digital telephone rlictrih -fin~ system of the preferred Pmho~1imrnf allows multiple telephone or data . ... --\:~ ~' ;- 'll devices to use a single connection to a main digital telephony switching device, such as a Private Automatic Branch Exchange (PABX). A telephone ~ system utilizing the preferred 21 ~594 1 Wl) 96103846 . ~ ' 2 I ~

c..,l-o~ 1 of the multi-nodal di~gital telephone d ~ J;'~ system of the present invention comprises a main telephony switching device, and a plurality of telephony control units, wherein each of the telephony control units is cormected to at least one telephone unit. A data link, comprising at least one data channel and a plurality of voice channels, cormects the telephony control units to the main telephony switching system in a daisy chain ~ The multi-nodal telephone .1~ ,., system of the preferred 1 1.~..l;....1 is based on P 'lloop" topology, where at least one daisy chained cormection of the telephony control units is comnected to the telephony control switch, which is a node on the loop. In addition, 8 detecting circuit is colmected to the data link to determine if the at least one data channel and at least one voice channel is to be received at the telephony control unit. The detecting circuit delays the of at least one data cha, nel without delaying the ~ of the at least one voice channel.
A method of controlling the multi-nodal digital telephone ~" ' ' system is disclosed. In a preferred r ' - " t, one data channel on the data link is used to connect each of the telephony control units to each other and to the main telephony switching device, t~s creating the "loop" topology. Control data from the telephony control unit or main telephony switching device, is transmitted on the data char,nel of the data link to each of the telephony control units. The data channel at each of telephony control units is sampled to receive the ~ on the data channel. The sampled control data on the data channel is decoded to determine if the data isdestined for the telephony cvntrol unit that intercepted the data. If the message is mtended for the L.~l~,~,ptill~ telephony control unit, the unit ret~uns the message for processing. If the message is not intcnded for the ~ /.hl~ telephony control unit, it sends it on to the next telephony control unit in the daisy chain. The control data from the last telephony control unit in the daisy chain is sent to the main telephony switching device on the data link for processing by the main telephony control switch. As each telephone unit checl~s the message to determine if the message is intended for the unit, the message is delayed. Delaying the data channel is not significant, as the user is usuaily urable to detect the delays in cnll set up tirne and . " However, if similar delays were allowed on the voice chalmels, the user would detect such delays =

~ W096/03846 ~ ~ 3 219594~ r~u~ 2i~

in the r ~ Lull. Therefore, once the data channel sets up a telephone call, it assigns one of the voice channels to the telephony control unit. The voice; ~r ~ received by the main telephony control switch is i ' on the assigned voice channels of the data linl; to the telephony control unit that initiated the call without being S intercepted by the other telephony control units. This direct connection of the voice channel with the telephone control units prevents the delays in the voice r- . .. ,;~
which exist in the data chalmel.
In the preferred ~ , the digital telephone ~ t,;~ ;,,,, system is in a cul~ ,;..1 airplane for passenger use. The reason for the multi-nodal approach in a ~ ' airplane ellvll~ is to reduce the amount of wire rcquired to connect a multitude of stations to a PABX. The reduction of wiring is important in an aircraft Cll~;lUIIIII.~, where wiring space and weight allowance is limited. Further, the installation of a phone system into an airplane is a very Cl ~ ' ' task due to the close quatters in an airplane. Therefore it is desirable to reduce the amount of wires that are used to connect the telephone system.

Brief De~crinti~ of the Drawings Figure I a block diagram of a preferred, I ' of a telephone ~ u ;' ,..1;....
system.
Figure 2 is a block diagram of a Cabin T~' ' Unit connected to a Zone Telephony Box which is in turn connected to a plurality of Seat TelephonyBoxes.
Figure 3 is a diagram of the layers of the, protocol on the D-channel.
Figure 4 is a block diagram of the circuitry of the Seat Telephony Box.
Figure S is a bloclc diagram of the circuitry of the Seat Telephony Module.
Figure 6 is a diagram of the sofnvare layers; ~ t I in the Seat Telephony Module.
Figure 7 is a ladder diagram which illustrates an example of the steps that occur from call initiation to call c"mrlPti"n ?~959~1 w0 96103846 ; . - f ~ ' 4 ~ 8 Detailed Description of the Preferred ~ .}~ tS
Figure I il}ustrates a block diagram of an exemplarv digital, system in which the multi-nodal digital telephone riieiTihlTti~n system is ;.. l L .. ,t.. l In the preferred ~ .. l.. ,l the multi-nodal digital telephone .I;~ - system is S ;..llll.... n J in a f ~ l airplane for passenger use. In the ~ ' aircraft cl.~..ul.lll.,llL, the overall digital ~ system is referred to as 8 cabin system (CCS) 10, which is designed to prctvide igh quaiity voice and data f ...... .~ ;... to, ~ ' aircraft passengers. The /u~ .t~c of the CCS 10 preferably cormects multiple voice snd fax/data chasnels to a plurality of 0 ICI,~ ~ 7/~ h ~ 7 12 on board the aircraft which establish a connection to worldwide ~ ;11.. networks, or bearer systems utilizing the preferred ~ ..l.o.l; . .; of the telephone l1ietih~tinn system. Preferably, the CCS 10 provides access to multiple bearer radio systems via the on board ICl.,..;~l;~h.. - ' ..- T' ~' 12 such as a North American Telephone System ~NATS), Satellite T-' Systems (SATCOM), and Terrestrial Flight Telephone Systems (TFIS). The CCS 10 preferablycompri~s a cabin i~' unit (CIIJ) 14 and a cabin d:~ ;l ;.... system (CDS) 16. The CDS 16 provides the necessrry interfaces between each of the telephone units used by the pas~ngers on the aircraft and the CTU 14. The CTU 14is an intelligent telephony switch that controls and routes telephone calls between the passengers and the bearer systems 12.
The CTU 14 is a digita, telephony switching device which controls and routes calls to and from the telephone units on the aircra* to one of the external bearer systems. The CTU 14 ~ , Private Automatic Branch Exchange ~PAe,X) r~ ;lY which is commonly used in multiple l;ne C~ teiephone ~ ~ - The CTU 14 provides thenecess~ry interfaces to, voice and data 1".. ~.. : .. ~ from the internal aircraft telephone system to the external bearer systems via a Primary Rate Interface (PRI~. Preferably, the CTU includes u~ill~ly three to fifteen Counsel of European Posts and Telegraph (CEPT) El PRI interfaces 18 to . with the ~ 12 of the digital bearer systems, such as the NATS, digital SATCOM. and TFTS systems, and at least one four-wire analog interface 20 to c.. , ~ with the analog 1~ of ~ W0~6/03846 i ~ 2195941 r~.,u~s/os~o the analog bearer systerms, sudh as the analog SATCOM system.
As illustrated m Figure 1, the CDS preferably comprises at least one Zone Telephony Box (ZTB) 22 and may comprise up to eight ZTBs. Each ZTB 22is connected to the CTU 14 via a data link 18. In a preferred e l " t, each ZTB 22 S is connected to the CTU 14 via an El interface 18. Each ZTB 22is connected to at least one telephony control unit, or Seat Telephony Box (STB)24 via a data link, such as an El interface 18. In turn, each STB is connected to at least one Arrn Rest Telephone (ART) 26 via a TTL serial com ection and analog, to the ear and mouth pieces on the Imes 28. More preferably, up to three ARTs 26 can be connected to each STB 24. Ad~ t. e~ ly~ utilizing the CDS 16 of the present invention an ART 26 can be provided at every seat on the airplane. This enables a greater number of passengers to have access for initiating telephone calls than many prior art systems.
In the preferred be " t, the ZTB 22, as illustrated in Figure 2, does not include any telephony elc~,l" The telephony electronics are located on the STBs 24 and on the CTU 14. The ZTB 22is utilized for wire i amd power ~li~ih~hnn to the STBs 24 amd their respective ARTs (Figure 1). For wiring Cv~ fi~ ,C the STBs24 are comnected in daisy chain loops to the ZTB 22. From theZTB 22, a loop 30is connected to a first STB 24 via an El interface 18; and in tum, the first STB 24is connected to a second STB 24 which is in turnconnected to a third STB24 which is in turn connected to further STBs24 umtil the end of the chain is reached. At the last STB 24 in a chain, a loopback plug 32is provided to comnect the outgoing transmit messages from the STB 24 to return wiring in the STB 24. For cv..~, the return wiring is routed through each of the STBs24 via the return wiring to the ZTB 30 and ultirnately to the CTU 14. However, as will be understood by those of skill in the art instead of looping the wiring through each of the STBs24 it is possible to connect the output of the last STB 24 in each chain directly to the input of the CTU 14. However, in a typical airplane C~l~;ll it is preferable to reduce the amount of wiring required, therefore the loopback method is preferred over the direct connection of the last STB 24 in the chain to the CTU 14.
Preferably, the ZTB 22 comprises up to four ~;1~1~11~1...1..~;11.1 Ioops 30 of STBs Wo 96fO3846 1~ ' - 6 2 t ~ 5 9 4 I r~ Gi21b 24 which are indicated on Figure 2 as STB LOQP 0, STB LQOP 1, STB LQOP 2 and STBLoop 3. In the preferred ~ V ~ twenty STBS 24 may be comnected to STB
Loops O and 2 and twenty STBS 24 may be cormected to STB LOOPS 1~md 3; thus forty STBS 24 are preferably connected to each ZTB 22. However, up to sixty four STB5 24 may be connected to and addressed by each ZTB. AS Will be recogni~ed by one of skill in the art, additional STBS 24 may be added to each ZTB 22 by increasing the number of address spaces reserved to address the ZTBS 22.
AS illustrated in Figure 2, it is possible to think of the ~ from the CTU 14 to each of the STBS 24 and back to the CTU 14 as a single large IQOP which is routed through the ZTB 22. In addition, the ZTB 22 transfers power from a power supply 33 to each of the STBS 34 and their respective ARTS (Figure 1) Dlong a set of power d;~ ' wires. With regard to power iictrih~ n, the ZTB 22 preferably routes 115 VAC at 400 Hz from a power supply through the ZTB 22 to the STBS 24.
The STBS 24 in turn provide power to their respective ARTS. In an alternate ~.. l.U.ii~ power is provided directly to each of the STBs 24 from the airplane's power supply. With regard to the between the CTU 14 and the STBS
24, an El i ~ (Tx) pair from the CTU 14 is preferably routed through the ZTB
22 along the dotted internal connection iine to STB Loop 0. In the preferred t~ , tne power hnes are routed on a cable 34 which also contains the .. "".. .: -~i,.. wiring. The STBS 24 in each of the STB IOOPS 3Q are configured in a daisy chain, whereby the first STB 24 in STB LOOP O receives data on its receiver (Rx) pair f rom the CTU's Tx pair 35;) and sends ciata to the next STB 24 in the loop 30 on its Tx pair ~to ihe next STB'S Rx patr). The last STB 24 in a IQOP has a loopback plug 32 attached to it that routes the Tx pair coming from the last STB 24 2~ back through ail of the STBs 24 in the IDOP 30 on a return cable 36 through passive c...,..~ on each STB 24. Once ~e Tx pair in STEi LDOP O is routed back to tbe ZTB 22, it is cormected to the frst STB 24 in the next STB IOOP 30 via a cable 34.
The El 1,.... ,.. signal finally emerges from the last STB 24 in the last STB IOOP
30, such as STB LOOP 3. The last El i signal is routed back to the CTU
14 on the ZTB's Tx pair in a retnrn cable 36 to the CTl;i~s Rx pair 38. Therefore, in order to enable proper connection of the STBS 24 to the CTiJ 14, if one of the STB

~ wo 96/03846 ~ 5 9 4 ~ 2 1 o loops 30 on the ZTB 22 does not have any STBs 24 then a loopback plug 32 must beplaced on the ZTB to STB loop cormector to complete the El circuit.
As discussed above, a primary rate interface such as a CEPT El interface is usedto connect the CTU l4 through the ZTBs 22 to the STBs 24. The CEPT E1 interface 5 is based on utilizing two twisted p~urs of wires to connect two devices to each other thus forn~ing a point-to-point interface. The clocking, and bit stream protocol for the CEPT E1 interface is described in Re.,.. "... l~ .. G.703 of the lr Telegraph & Telephone C~ ' ~., Committee (CCITT), as is well known to tbose of skill in the art and is hereby ;A~ d by reference. The interface is run at 2048 Kilo-bits per second (Kbps). The bit stream is broken up into 32 channels, each providing 64 Kbps throughput. Ofthe thirty-two channels available on the El interface, a first charmel is used for framing the ~ , i.e., delimiting each frame. The sixteenth channel on the E1 interface, also referred to as the D-channel, is utilized as the signaling link between the CTU and each of the STBs to request and negotiate call setup or call clearing and other signaling activities. The other thirty cha.-nels, referred to as Bearer channels or B-charnels, are used as: linlcs to transfer voice, voice-band data, and packet data from the ARTs to the CTU and ultimately to the bearer systems. A.l~ ,,. v ~ly, by utilizing the E1 interface up to thnrty of the ARTs may be utilized at the same time, because thirty B-channels are available to connect telephone calls. This is a sigmficant advantage over the prior art systems whichenabled fewer telephone units wbich shared the same wiring to be operated at the same time.
In order to keep track of the ~...,. - - - - - ;....S on tne D-channel, link access protocol over the D-Channel (LAP-D) is utilized. As illustrated in Figure 3, the traditional model for depiction of a ~ , protocol is to use a "stack" model, where each logical layer of the protocol is shown as a "box"t with the stacked on top of each other, from the bottom, up. The .,-- ,.". ~ protocol on the D-channel is broken up into a plurality of layers, the first layer (L1) or physical layer 44, the second layer (L2~ or the data link layer 44 and the third layer (L3) or the network layer 46. As indicated above, the physical layer 44 is described by the CEPT
El standard, which is hereby ih~ ' by reference. In the preferred . .. ,ho.l;,,.. .,l = ~

wos6~3s4~ 8 2 1 9 ~ 1&

the data link layer 45 of the protocol is described in the CCITT R~-.. l-~;, Q.921, which is hereby i.l~vll ' by reference. Thc network layer of the preferred is described in CCITT R~ - Q.931, which is hereby ;11~ VIIJVl~ by reference. The above protocol standards which have been ;... A ~by reference are well known to those of skill in the art. The collection of the CEPT El physical layer 44, the Q.921 data link layer 45 and the Q.931 network.layer 46 is sometimes referred to as the ISDN protocol. In addition to the standard portions of the protocol, the STBs 24 include a soflware layer which enables severnl STBs 24 on a loop to use the same physical medium to ~ with each other. This software prograrn layer, which will be described in more detail later, is called a Medimn Access Control (MAC) layer and provides the point tv multi-point ~ . . .L,. .- .1 of the telephone ~li~ih~lti~n system. As described bdow in association with Figure 6~ the MAC layer is located between the physical layer and the data link layer. The MAC layer performs the arbitration among all of the STBs 24 on the loop which want to use the D-channel for signalling.
Figure 4 illustrates a block diagram of the clectronics rcsidcnt on each of the STBs 24. The elcctronics provided on each STB 24 preferably comprises a Seat Powcr Module (SPM) 40 and a Scat Telephony Modulc ~STM) 42. As described above, power lines 48 and El i lines 18 are routed from the ZTB (Figure 2) to a first STB in a loop. The power lincs 48 from the ZTB are routed to the SPM 40 which converts the A/C power received from the ZTB to DC power. The SPM 40 routes the DC power to the respective ARTs along line 50 and to the STM 42 along line 52. The El lines 18 from the ZTB are routed to the STM 42. The STM 42 controls the telephony functions of the ARTs. Links are set up between each of the ARTs to the STM 42 to transmit and receive voice ;,.r.. ~f; - data and command;.,r.. ,- ;.. tolfrom the ARTs along lines 62 and 64. Outgoing El d~da from the STM
42 on lines 68 as well as the power from the Seat Power Module 40 on lines 48 are routed to an external connector on the STB 24 and are transmitted along lines 72, 48 lc~ ly to the next STB in the cham or to the CTU if the STB is the last module 30in the chain.
Figure 5 illustrates a more detailed functional block diagram of the hardware on ~ wo 96103846 . ~ 18 the Seat Telephony Module (STM) 42. The El interf~e 18, i.e., the Rx t,.- ~"pairs 74 and the Tx 1~ , pairs 76, is connected to the STM 42 via a reiay 78.
The relay 78, when set, enables the El interface 18 to connect to the hardware of the STM 42. However, if the STM 42 is not r, ..1:....~ properly or if it is desired to disable the STM 42 functions for a group of users, the relay 78 can be opened and the El 18 connection is terminatcd.
Assuming that the El interface 18 is connected through the reiay 78, the i.,r.". ~;.". on the iRx pair 74 is received by El interface hardware 80. The Elinterface hardware 80 preferably comprises a framer 82 and an LIU 84. The input Rx signal on the line 74 is transmitted first to the framer 82. The framer 82, typicaily a crystai and associated logic, is utilized to dirfu.~ e~h of the charmels as they are received from the El interface 18. The Rx signal is then transmitted to the LIU 84, which converts the El signais from the voltage level required for E1 l~ to a voltage level that is acceptable to the hardware in the STM 42. After the El interf~e hardware 80 converts the bit stream received from the E1 interface 18 to signals that are . ~ by the STM 42, the El interface hardware 80 sends the signals received on the D-channel to the CEPT El transmit and receive (XCVR) hardware 85.
The CEPT XCVR 85 utilizes the High Level Data-link Control (HDLC) protocol, which describes how to assemble a collection of octets, i.e., 8-bit values, to form a complete HDLC message. The HDLC interiupt hardware acts in association with the XCVR 85 to interrupt a III;~.IUI./IV-,-~...Jl 86 when a complete message is received. Preferably, the HDLC interrupt hardware is resident on the 1118,1U~/IU~,~,...,V~ 86. In the preferred ..,1 ~o~l .. ,.. ,l a Motorola 68302 IllI~lU~/lU~ )l which bas tne HDLC interrupt hardware on the VIJI U~ DDVI is utilized.
Referring also to Figure 6, the CEPT XCVR 85 preferably comprises a receive (Rx) queue 87 and a transmit (Tx) queue 88. The Rx queue 87 collects the data received on the D-channel and groups the data into the HDLC message packet format which is readable by a l.l;~,lU~JlU-,.,..~.Ji 86. The Tx queue 88 receives messages from the ~liwvlJlu~aDvl 86 via the XCVR Tx queue service request routine (XCVR SQR) 89 and transfers the next available message m the Tx queuc 88 imto the .I~ lu~ e bit stream format required by the t,.---- -l: ~ ... standard. Once a complete message has 2~ a~oA 1 W096/0384~ . r~."Ja. .c,~i& ~
been received by the Rx queue 87 on the CEPT XCVR 8~, an XCVR initiated HDLC
interrupt service routine (XCVR ISR) 90 is initiated. The MAC layer software 91 running on the ~ UlJIV~ ...Ul 8G determines if tne message received from the D-channel is intended for this STM 42. If tbe message received by the STM 42 is intended for the STM 42, the XCVR ISR 90 stores the message until the IlI;~.lU~llU~.~.,vl 86 is avaiLable to act on the message. If the message receiYed is not intended for this STM 42, &e XCVR ISR 90 on tne llllk.lU~lU.,~ .II 86 routes themessage to the XCVR SQR 91, for delivery to the Tx queue 88. The message is stored in the Tx queue 88 until the D-channel becomes available. Once the D-charmel becomes available, tbe message is sent through the LIU 84 and framer 82 im order to adjust the voltage and clocking of the signal to the El standard of i and the message is sent along Tx pairs 76 of the El 18 to the next STB.
The MAC lsyer 91 may be ~ Sd in at least two distinct operational modes: the store-and-forward mode and the polling mode. In the preferred ~ _L
the MAC layer 90 is ,' ' in the store-and-forward operational msde. In the stsre-and-forward mode, each STB 24 intercepts all D-channel messages. When a complete HDLC me~sage is received by the XCVR RX queue 87, the XCVR intelrupt service routine 90 is invoked ts move the message from the XCVR RX queue 87 to the MAC layer queue 9t in the UIJIV~_..Ul. The intercepted message from the upstreamSTB 24 (closest ts the CTU) are looked at by the MAC layer 91. If the packet is a broadcast message, ~i.e., if the message is sent to all of the STBs 24, the message is sent to the L2 layer 92~ and a copy of the message is put back on the XCVR Th' queue 88 via the XCVR SQR 89 for ~ the du.. STB 24 (ts the next STB).
If the message is addressed to this STB 24, the MAC layer 91 sends it directly to the L2 layer 92. If the message is not addressed ts this STB 24, it is put back into the TX
queue 88 via the XCVR SQR 89~ In all cases, the XCVR TX sueue 88 will remove a message from the~head of the queue (least recent~ and send it out on the D-channel once it is available. Therefore, in the store-and-forvard mode the messages on the D-charmel will be delayed by each STB 24 for some period of time. Presently, the ~ delay caused by the STB 24 checking to see if the D-channel message is intended for it and then passing the i"r.. A;"" onto the next STB 24 is 16 frames.

~1 ~594t ~ WO 96/03846 , ~ I / L ~, ', ~ 16 In an alternate ~ ' " t, the MAC layer 91 is . ' ' in tne polling mode. In polling mode, tbe XCVR hardware 85 will "spy" on tbe D-channel by ~cf~nhlinz local copies of the messages received from an upstream STB 24, and passing t. e D-channel bit stream through Imh~ r~ With each received message, aninterrupt will invoke the XCVR irterrupt serYice routine 90 which will send the message to the MAC layer 91. The MAC layer 91 will look for a polling message addressed to the STB 24. Any other message not addressed to this STB 24 is thrown away. Once a polling message addressed to tbis STB 24 is received from the CTU 14, the MAC layer 91 will instruct the XCVR hardware 85 to intercept all D-charmel messages until further notice. It will also instruct the XCVR SQR 89 for the XCVR
TX queue 88 to commence its ~ operation for the next queued message.
While in this mode the MAC layer 91 will retransmit all messages from upstream STBs 24 which are not addressed to tnis STB 24 by putting them on the XCVR TX queue 88. If a broadcast message is received, it is copied and passed to L2 layer 92 as well as forwarded to the next STB 24. If the broadcast message received is an order to go into store-and-forward mode by the CTU 14, then tbe MAC layer 91 will assume tbe Store and Forward mode until further notice. Otherwise, if a Polling message addressed to another STB 24 is received, the MAC layer 91 instructs the XCVR hardware 85 to go into "spy" mode, and instructs the XCVR SQR 89 for the XCVR TX queue 88 to cease 1-~ g any more messages. In the poling mode, the CTU 14 is constaDtly switching between each STB 24 as it polls for data. During the time period that the STB 24 is polled, the STB 24 is constantly 1.~ ;..g its data until the CTU 14 polls the next STB 24.
Regardless of the ultimate operational mode of the MAC layer 91, during the system i" ~ ;"", the CTU 14 utilizes the store-and-forward mode to broadcast a .~5;DhaLiull request to all the STBs 24. During the ~ ha~iul~ request, each STB 24 informs the CTU 14 that it is operable and where it is located on the loop. This is ~- - u.l.~ by each STBs 24 in turn sending their response to the 1~ tldtiUII request, along with the responses from the other upstream STBs 24 to the CTU 14. Once hhel~g;.~ iUII is completed, all STBs 24 are assigned Terminating Endpoint Identifiers (TEls), i.e., addresses on the loop. At this point, the MAC layer 91 will remain in the 95~94 1 w0 96/03846 12 , ~ .,r~

store-and-.~orward mode for tne remainder of the system operation, unless the CTU 14 indicates otherwise.
In order to enter the polling mode, the CTU 14 will broadcast a commence polling message to all STBs 24. Thc MAC layer 91 will then instruct the XCVR
hard-vare 85 to only "spy" on the D-channel traffllc, as described above. The MAC
layer 91 v.~ill still assemble and send a copy of the received messages to thc XCVR RX
interrupt service routine 90, but it does this in parallel with other STB 24 vhich are also listening to the D-channel. Also in polling mode, tbe XCVR service request routine 89 for the TX queue 88 will be instructed not to send any other ;..f.
dun~ ~l to other STBs 24.
Regardless of the mode that the MAC layer 91 is operating m, if the mcssage is intended for the STB 24, the STB 24 transfers the message to the link Q.921 L2 layer 92. Once the L2 layer 92 is available, the L2 layer 92 acts on the message. If the message received by the L2 layer 92 also requires action by the Q.931 L3 layer 93, the message is stored until the IlI;~lUJJlU~vUI 86 has the ~~ r to act on the Q.931 L3 layer 93 of the software. Once the L3 layer 93 be~aomes available, the L3 layer 93 acts on the mwsage. If the message received by the Q.931 L3 layer 93 also requires action by the ~ ';.... layer (not shown), then the l.._lVIJ~U~....Ui 86 saves the message until the r. ,~' Iayer is able to act on the message. Once the upper-most layer has completed ~the required action on the message, if a response to the CTU 14 is required, the resp~se message is sent back down through the software layers until the MAC layer 91 is reached. The message is received at the MAC layer 91 and sent to the XCVR SQR 89 for i via the XCVR TX queue 88 to the El interface 18.
Referring back to Figure 5, in addition to the D-channel int~rf~rinf, the fi~lu~Jlul.. J ~Ul 86 receives and transmits signals from the ARTs 26. Preferably, the IIIIL~IU~/IU~ UI 86 is connected to each of the ARTs via a TTL UART 94. When a key on the telephony keypad is depressed on the handset, the ART sends a signal to the STB, which is received by the UART 94 on the ~TM 42. Once a s;gnal is received by the UART 94, the UART 94 interrupts the Illl~lUylU~ UI 86 with a message in an ~ ASCII format from the ART. If the message received OD the UART 94 from the ART

~ w0 96~038~6 ~ 2 t 9 5 9 4 1 r~ c l j~ O

requires action by the CTU 14, such as a call initiation sequence or a call discoMect signal, the Illi.,lUJJlU.,I,~Ol 86 processes the UART message and sends an ayl~
message to the CTU 14 on tbe D-channel, as indicated above. The additional hardware on the STM 42 is preferably used to transmit voice and modem data from the ART 26 through the El interface 18 to the CTU. 14 Preferably, a c~d.,ld~cod~ . (CODEC) 95 is com~ected to each of the ARTs at one end and to a Time Division M~
(TDM) 85 at the other. Preferably, the CODEC 95 converts voice data, which is anaudio signal, to a digital signal that can be processed by the TDM 98. The CODEC 95 also converts the digital signals received from the TDM 98 to audio voice signals, which are i ' to the ARTs. Preferably, the TDM 98 controls tbe receipt and delivery of the voice data to/from the ARTs from/to the CTU 14. Further, a modem/fax port on each ART is connected to a CODEC loop detector 96 for translating the analog signals to digital signals and visa versa. The CODEC loop detector 96 is also coMected to the TDM 98. Preferably, the TDM g8 is an Extended Phone Interface Chip (EPIC~. such as a Siemens PEB-2055. Additionally, the UIJIU.,.,~JI 86 is connected to external control logic 100, flash memory 101, and RAM memorv banks 102. F nally, the STM 42 includes passive wiring that routes the return signals, i.e., receive ('.'~) and transmit (Tx) p~urs 104, which are routed from the last STB in the loop back to the ZTB. Therefore, the Rx pairs that are received by the STM 42 on the return route are i " 'y routed to the Tx pairs on the STM 42 and then to the next STB via the E1 interface. Ultimately, the message is routed back to the CTU.
When a call has been initiated, the CTU assigns one of the B-chaMels to the STM 42 for i audio data to and from the ARTs. The CTU sends a message on the D-channel to the STB indicating the chaMel ~ei~nm~nt The TDM 98 on the STM 42 that initiated the call then activates a hardware connection between the CODEC g5 assigned to the ART that initiated the call and the El interface hardware 80 in ~IC,.J~ t;UII for the receipt of the ~ from the assigned B-chaMel.
The E1 interf~e hardware 80 on the STM 42 monitors the signals l..~ . .1 on the El interface 18 and looks for data on its assigned B-channel. Data bits on the B-chaMels that are not assigned to the STM 42 are transmitted through the STB with only a one frame delay which is caused by the El interface hardware 80 on the STM

W096/03846 ~ I =' i 14 L 3 ~ J ~
42 checking eûch B-channel as it passes through the STB to determine if thc channel is assigned to this STB. As soon as the ;..r."...,.~ . is received by the STM 42 on thc assigned B-channel, it is ' '~, converted to the proper format, i.e., voltage and clock rate7 by the El interface hard vare 80 which can be received by the TDM 98.
The B-charmel ;.. r~.. - ;.. is routed through the TDM 98 to the uylJlu~ , CODEC
95 that is connected to the ART that initiated tho call. Preferably, the i..r .. ;.... on the B-channel is routed tbrough the El interface hardware 807 the TDM 987 and the CODEC 95 hardware to the ART without sigmficant delays. Vo;ce data received at the ART is routed through the dedicated CODEC 95 to the TDM 98 and is i ' ' from the TDM 98 to the El interface hardware 80 for irnmediate connectiûn to thededicated B-channel for receipt by the CTU. By proving direct routing of the incoming assigned B-channel signals through the hardware and by or ly ..lt.l~~ g the B-channel for one clock cycle per STB to determine if the; r~ -7l, is intended for this STB, the voice ;..rl- ...~ can be received and transmitted through the system without any notable delay to the user.
Referring also to Figure 7, a ladder diagram is provided to illustrate an example of the steps that occur from call initiation to call rrmr1~inn Typically7 the phone call is initiated on the ARl' by a passenger who completes a series of initiation steps7 such as pressing the on button7 entering a credit card number, etc. The initiation message lû6 from the ART 26 is sent to the STB by signals received through the UART 94.
The UART 94 interrupts the llfi~ UV~I 86, which receives the call initiation message 106 frûm ~e ART 26. The IllI~.lUlJlU~7vl 86 processes the received from the ART 26 and transmits a phone call request message 108 to the D-channel Tx queue on the CEPT XCVR 85. Once the D-channel becomes available, the message from the CEPT XCVR 85 is transmitted through the LIU 84 and the frarner 82 in order to adjust the voltage and clocking of the signal to the El standard of 1l. .~... - ... The phone call request 108 is then sent on the D-channel from the initiating STB 24 to the next Cul~.utin;; STB 24 on the El transmit (Tx) pair. The next STB 24 reads in the message 108 on the D-channel through its receive (Rx) pair of lines. The messa~e 108 on the D-channel is sent to the framer 82 and the LIU 84 to transfer the message to a voltage level and frequency that can be received by the ~ ~ 2195941 ~ W096/03846 ' i ~ 5 r~,u,. ,~lX
STB 24. The message 108 is collected by the receiving queue on the CEPT XCVR 85.When a complete message has been received, the HDLC generates an interrupt to the Illl~.IU~JIU~....Ol 86, which runs an interrupt service routine to decode the message 108.
Once it is determined that the message 108 is not destined for this STB 24, the S Illh~lU~/lU~ aVI 86 sends the message lû8 to the transmit queue on the CEPT XCVR
85. Once the D-channel becomes available, the message 108 is sent through the LIU
84 and framer 82 and through the Tx pairs on the STB 24 to the next STB 24. Thisprocess of message checking by each STB 24 continues until the message is received by the CTU 14.
The CTU 14 processes the initiate phone call request 108 and assigns one of the B-channels as the t media for the call. In this example, the CTU 14 assigns chalmel 17 to the call request of the initiating STB 24. The CTU 14 sends a message on the D-channel to the first STB 24. As described above, the first STB 24 checks to see if the message 110 on the D-channel is intended for its receipt. After the STB 24 determines that this message 110 is not intended for it, the first STB 24 sends the message 110 out on the D-channel to the next STB 24. The message 110 traYels through each of the STBs 24 until it reaches the requesting STB 24.
Once the message 110 reaches the initiating STB 24 on the D-channel, the ~II;-~IUI.IIU~ Vl 86 on the STB 24 determines the message 110 is intended for it. The III;~.IUI~IU-~ 86 processes the message from the CTU 14 and determines that the B-channel on charmel 17 is assigned to the call. The ll i~.lvl~lu.,C..~I 86 sends the channel assignment ;"r~ 1;..., to the TDM 85. The TDM 85 sends a message to the El interface hardware 80 indicating that all i..r~ received on channel 17 is to be directly routed to the TDM 85. The TDM 85 in effect sets up a hardware connection between the CODEC 95 assigned to the initiating ART 85 and tne El interface hardware 80 m ~l~ ~dliuil for the receipt of the ~;.... , 8~ - ;..,. on charmel 17.
With this connection made, a message 112 is sent to the ART 26 to indicate a call can be made on the assigned channel. Next, the passenger dials the requested phone number 11-4. on the ART which is sent to the STB 24 via the TTL serial interface. The phone number 114 is received by the UART 94 and is sent to the - ~ 2~ 95~4 WO 96103846 ~6 III;~,IU~IU~ VI 86. The ~ V,U~V~.C~vl 86 trnnsfers the dialing; r-, X.." to tho Q.931 software. The Q.931 sofiwaro sends tho dialing i .f~ . to the Q.921 layer.The Q.921 layor sends the dialing i.r,.". ;-- to the CEPT XCVR 85. From tho XCVR 85 the data is sent to the El interfaco hardware 80 and then on the D-charmel S of the El 18. As discussed abovo, tho phono number mcssago 116 from tho initiating STB 24 is sent along tho loop to next subsequont STB 24, whoro it is A~tl~rmin~A~ that tho messago 116 is not intended for that STB 24. The STB 24, in turn, sends the messago 116 on to the other STBs 24 in the chain until it reaches the CTU 14. Once the CTU 14 receives the phone number message 116, it establishes a connoction with the external bearer system. Once the connection is made, the CTU 14 transmits the connecting i.,r,.,.. ~;.... 118 on the D-charnel to the first STB 24, which passes the connecting; f"..,-l;.... 118 on until the initiating STB 24 roceives the connection i ,.rl,. ., - i ,., 118 on the D-channel.
The cormection i~ ;.... 118 received by the initiating STB 24, informs the IS STB that the listenor can use tho assigned B-channol, i.o., channel 17. While the call is connected, all voice and data j"c"", ;,~" 122 regarding the current call is sent to from the ART 26 and through each Or the STBs 24 along the B channel, i.e., channel 17, to the CTU 14 and vice versa until thc call is A' .. -- .. '.. 1 However, as discussed above, the STBs 24 that nre not assigned to the B-charmel ' ly reroute the ;, . r .. ", - .;". . on the B-channel to the next STB 24 and ever~ally to the CTU 14 causing an i ~.g,.;r;.~." dolay in the ~ of the voice i ,f .. x, After the c~ Liu-l has ended, the user initiates a terminate call sequence on the ART 26; for example, the user presses the LND key on the handset. This .,.. message 124 is sent on the TTL serial channel to the STB 24. The data is received by the UA~.T 94 on the STB which interrupts tho Illl~IU~ .,JI 86. Tho u. Vl".J~ -~" 86 procossos tho message 124 from tho ART 26. The IIII~IU~J~U~_..Jl 86 transmits a terrminate message 128 on the D-channel to the CTU 14. Tho mossago 128 is recoivod by oach of tho subsequent STBs 24. Once the STB 24 deterrnines that the message 128 is not intended for it, it will pass the message 126 along the chain until the message 126 is received by the CTU 14. Tho CTU 14 will terminate tho call with the bearer system.

J3C,~ 21~941 ~ W0 96J03X46 ~ r t7 ~ 2111 Next~ the CTIJ 14 sends a message 128 to the STB 24 indicating that the reserved B-channel, i.e., channel i 7 in this case, is d ' and therefore available for other users. The first STB 24 receives this message 128 and determines that the message 128 is not intended for it. The STB 24 sends the message 128 to the nextSTB 24 in the chain. Once the initiating STB 24 receives the message 128, the ...;~ v~,.u ~ - .. 86 receives and process the message 128. The Illi~lU,UIU~ .JI 86 sends a signal to the TDM 85 and to the El interface hardvvare 80, indicating that theecignmPnt of channel 17 to the STB 24 should be i ' The TDM 85 will break the link between the CODEC 95 and the El interface 18 tbat was reserved fûr channel 17 l-.. .~.. .: . . .. ..~
Ad~ ~J.- ~l~, the CDS of the present invention reserves one of the B-chamlels for each telephone Cu~ dtiul. that is initiated. By preventing other STB's from il.t~,l.uluL,..g the voice 1.. .--..~ on the B channel for an extended length of time I .y and unwanted delays in the voice, - are :" ' Further, by using a primary rate interface, such as an El ~ ; - . interface, the data deliverv rate is fixed, so the voice ~ is delivered at a predictable rate. By providing an interface vith a known data delivery rate, problems associated with;- delivery timesofvoice messages are eliminated. These l I
delays are common with other packet networks, such as Ethernet and Token Ring systems. In additior., by ~" _ the number of devices that inte~upt the voice unwanted delays, which cause difficulty in telephony . are reduced to 1 t~ Ievels in the system. Other messages that are not a part of the audio ~ul~ l~Lion are delivered along a separate data charmel, i.e., the D-channel, which is i................. ~ulJk~ c~ However, such delays are generally acceptable in data delivery.
Further, the loop crnf~, ' of the Cabin Distribution System (CDS) reduces the number of wires required to connect the telephony system of the present invention.
The present invention may be embodied in other specific forms without departing from its spirit or essential cl.~t.,.;~Li.,~. The described c...l,o," are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than the foregoing 11, e~ipti~n All changes which come ~vithin the meaning and range of e.~LIivc.l~.ll.,~ of W~ 96103846 ~ 1 ~ ';
18 ~ I r~J,, the claims are to be embraced within ~eir scope.

Claims (10)

1. A telephone communication system, comprising a main telephone switching device;
a plurality of telephony control units;
a telephone unit connected to call of said telephony control units;
a data link comprising at least one data channel and a plurality of voice channels, connecting said telephony control units to said main telephony switching device; and a detecting circuit connected to said data link which determines if said at least one data channel and said at least one voice channel is to be received at said telephony control unit, wherein said detecting circuit delays the transmission of said at least one data channel without delaying the transmission of said at least one voice channel.
2. The telephone communication system as defined in Claim 1, wherein said telephony control units are connected to said main telephony switching device in a daisy chain connection.
3. The telephone communication system as defined in Claim 1, additionally comprising:
a plurality of transmitters/receivers connected to the main telephony switching device to establish a connection to a bearer system.
4. The telephone communication system as defined in Claim 1 wherein said data link is an E1 interface.
5. A method of operating a telephone unit, wherein said telephone unit is connected to a multi-channel communications cable comprising at least one data channel and a plurality of voice channels. said method of operating a telephone unit comprising the steps of:
delaying said at least one data channel to monitor the need to connect said telephone unit to one of said plurality of voice channels; and transmitting said plurality of voice channels through said telephone unit with minimal delay during said delaying step.
6. A method of controlling telephone connections in an airplane telephone communication system, wherein said communication system comprises a main telephone switching device, a plurality of telephony control units, each of saidtelephony control units connected to at least one telephone unit, a data link comprising at least one data channel and a plurality of voice channels connecting said telephony control units to said telephony switching device, said method of controlling telephone connections comprising the steps of:
transmitting control data from said main telephony switching device on said at least one data channel of said data link to the first telephony control unit;
intercepting said control data on said data channel at each of said telephony control units;
decoding said control data at each of said telephony control units to determine if said control data is destined for the telephony control unit that intercepted the control data;
sending said control data that is not intended for the intercepting telephony control units to a subsequent telephony control unit on said data channel;
sending control data from a last telephony control unit to said main telephony switching device on said data channel;
assigning one of said voice channels to one of said telephony control units for processing a telephone call;
transmitting voice information received by said telephony switching device to one of said telephony control units on said assigned voice channel; and transmitting voice information received by one of said telephony control units to said telephony switching device on said assigned voice channel.
7. The method of controlling telephone connections in an airplane telephone communication system as defined in Claim 6, wherein said plurality of telephone units and said main telephony switching device are connected via said data link in a daisy chain.
8. The method of controlling telephone connections in an airplane telephone communication system as defined in Claim 6, further comprising the step of:
processing said control data that is destined for the intercepting telephony control unit at said intercepting telephony control units.
9. The method of controlling telephone connections in an airplane telephone communication system as defined in Claim 8, further comprising the step of:
establishing a connection between said main telephony switching device and an external bearer system.
10. A multi-nodal digital telephone distribution system, wherein said telephonedistribution system comprising:
a multi-channel communications cable comprising at least one data channel and a plurality of voice channels;
a plurality of telephone control units, wherein each of said telephone control units is connected via a transmitter/receiver device to said multi-channel communications cable; and a medium access control software program in communication with said transmitter/receiver device on each of said telephone control units to arbitrate the access of the telephone control units to the data channel on said multi-channel communications cable.
CA 2195941 1994-07-26 1995-07-21 Multi-nodal digital telephone distribution system Abandoned CA2195941A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US28078294A true 1994-07-26 1994-07-26
US280,782 1994-07-26
US37073295A true 1995-01-10 1995-01-10
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US7020708B2 (en) * 1999-05-14 2006-03-28 Cingular Wireless Ii, Llc Aircraft data services
US7177939B2 (en) 1999-05-14 2007-02-13 Cingular Wireless Ii, Llc Aircraft data communications services for users
US6760778B1 (en) 1998-09-09 2004-07-06 At&T Wireless Services, Inc. System and method for communication between airborne and ground-based entities
US7548725B1 (en) * 2002-09-23 2009-06-16 Rockwell Collins, Inc. Null bearer system and method of connecting E1 data to the public switched telephone network
US7099665B2 (en) 2003-01-27 2006-08-29 The Boeing Company Apparatus and method for providing satellite link status notification
US7978603B2 (en) 2006-10-10 2011-07-12 Qualcomm Incorporated Traffic optimization in a heterogeneous wireless cabin network

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