Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04M—TELEPHONIC COMMUNICATION
  • H04M9/00—Arrangements for interconnection not involving centralised switching
  • H04M9/02—Arrangements for interconnection not involving centralised switching involving a common line for all parties
  • H04M9/022—Multiplex systems
  • H04M9/027—Frequency division multiplex systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04M—TELEPHONIC COMMUNICATION
  • H04M9/00—Arrangements for interconnection not involving centralised switching
  • H04M9/02—Arrangements for interconnection not involving centralised switching involving a common line for all parties
  • H04M9/022—Multiplex systems
  • H04M9/025—Time division multiplex systems, e.g. loop systems

Definitions

• This invention relates to a telecommunications system for voice or data to replace. the lines of a telephone system.
• Prior art telephone systems utilize a pair of wires from each telephone set to a central office that connects one telephone to another using a central switch.
• These prior art telephone systems require expensive cables running long distances and expensive support equipment and a central switch that interconnects the telephones. Further, these cables require special care because of their susceptibility to adverse weather conditions.
• My invention embodies an electronic circuit adapted to be connected to a cable and to a plurality of telephones.
• the invention allows each telephone to communicate with the others in the same cable without the use of long pairs of wires and without the use of central office equipment.
• Central office equipment would be used only if a call is for a telephone not connected to the cable and coming from another office.
• My system reduces the number of telephone poles substantially that would be required to support the same number of telephones.
• the cable such as a coaxial cable has a wide bandwidth. It can accommodate several signals at the same time in a concept well known in the industry, called Frequency Division Multiplexing (FDM) or Time Division Multiplexing (TDM). This concept has been used for many years to transmit different signals simultaneously over the same cable from one point to another.
• the cable is divided into channels and each signal uses a channel.
• My invention uses these well known techniques, but it dynamically allocates those channels (created in FDM or TDM) to different users.
• the essence of my invention is in the interface electronics connected between the cable and each telephone set.
• the board allows the phone to select a channel available for use by the initiating phone (transmitting) and send a signal to the telephone (receiving) to use the same channel. This information is sent in a special data signaling channel that every telephone is equipped with.
• the board has a transmitter and a receiver capable of changing their frequencies using a Phase Lock Loop (PLL). These frequencies correspond to the different channels allocated in the cable.
• PLL Phase Lock Loop
• a microprocessor in the board changes the transmitting and receiving frequencies. The microprocessor further selects an empty channel for the call.
• One of the channels is used as a communications channel among all telephone boards and the central office.
• the microprocessor in the associated board with that phone selects a channel pair and communicates through the data signaling channel to all the telephones which the communications channel has selected. All telephone boards update the channel's free status in order to prevent any other telephone from using it.
• the calling telephone sends its number, the called telephone number and the selected channel.
• the called telephone replies back as to whether it is busy or not. If it is not busy, the communication is established.
• a PC board in the central office connects the telephone to and. outside the telephone network.
• My invention broadly comprises a telecommunication system for voice (telephones), data or video using a distributive switching technology (DST).
• DST distributive switching technology
• Figure 1 is a schematic of single phone interconnected to a board connected to a coaxial cable
• Figures 2a and 2b are schematics of a dual cable tree topology
• Figure 3 is a block diagram of an interconnected board
• Figure 4 is an illustration of a frequency band plan
• FIGS. 5 and 6 are illustrations of a communications format
• Figure 7 is a flow chart of the calling and called telephone sequence. DESCRIPTION OF THE PREFERRED EMBODIMENTS )
• a telephone 2 is connected to an interconnect board 4 which in turn is connected to a coaxial cable 6.
• the phone 2 is a standard telephone commonly in use today having the standard two-wire or two line.
• the cable 4 is standard material having a conductor line surrounded by a conducting tube held in place by insulators.
• an analogue version of a distributed switching network of my invention is shown generally at 10. It comprises coaxial cables 11 and 12 to transmit and to receive respectively.
• the coaxial cables 11 and 12 have a frequency allocation plan as shown in figure 4, which allows 10Khz per channel.
• Each telephone conversation requires two channels.
• the call originator transmits on an odd channel and the called phone responds on an even channel.
• a repeater amplifier as commonly known in the art, such as used with a Cable TV distribution system, is placed in line in the coaxial cables.
• a dead end 14 is formed and interconnects the transmit and receive cables in the central office such that what is transmitted by all telephones in service in one direction will be received by all telephones through the other cable in the other direction.
• a Directional coupler 18 connects branch coaxial cables 16 and 17 to the main cables 11 and 12.
• An electronic printed circuit board 20 connects each telephone pair 21 to the coaxial cables 11 and 12 (or 16 and 17).
• the coaxial cables are each held by a steel cable (not shown) connected between the poles.
• the steel cable has plastic hangers (or other suitable material) that holds the coaxial cables in place.
• the steel cable is used to transmit an electrical ground for all boards plus a negative voltage for the system.
• PC board 22 At the Central office there exists a PC board 22.
• the boards are connected to the coaxial cable that runs from the dead end 14 to a terminating register 19.
• Each board 20 connects one telephone to the outside office if the call is to go to another area.
• the PC board 20 comprises a hybrid IC 30 such as a Motorola MC3419.
• This IC 30 isolates the signal received by the phone from the signal transmitted by the phone.
• the IC 30 is joined to a REC expandor 43, a transmit compandor 32 and a microprocessor 35.
• the compandor 32 such as an Exxar XR2216 compresses the signal and increases low level signals such as a soft talker user and reduces the level talker user signal.
• the VCO - Modulator 33 such as an Exxar XR 205 is a multiple use device that covers a wide range of frequencies, modulates them in AM, DSB or FM and provides a sinusoidal output.
• a Phase lock loop (PLL) 34 such as Motorola MC 145106 is a feedback loop that generates a correction voltage if the internal reference counter differs from the microprocessor selected number. This IC 34 forces the VCO 33 to be in the desired frequency.
• An oscillator 31 such as National 555 or 556 sends a dial tone or a ring back tone as the microprocessor requests it.
• a Frequency Shift Key 36 such as Exxar XR-2206 function generator transmits microprocessor information (such as telephone called, telephone status, etc.) to all other telephones and to the Central Station in the data signaling channel.
• microprocessor information such as telephone called, telephone status, etc.
• An FSK Receiver 38 such as EXXAR XR-2211 receives the FSK signal and decodes it.
• An Amplifier 40 such as National LM 324 amplifies the receive signal from the coaxial cable.
• a balance mixer such as Motorola MC 1496 combines the Receive Channel VCO 44 frequency and the incoming frequency.
• a low Pass Filter such as Two LM324 operational amplifiers is used as an active filter.
• a limiter and discriminator such as Motorola MC 3357 demodulates the signal coming from the filter.
• AGC automatic gain control
• the AGC comprises of two transistors such as AN 2222. ⁇ An expandor 43 that expands the compressed signal to the normal user amplitude range.
• a signal EM 50 that is used only in the PC board to interface with another telephone truck. Those wires are not used when the PC board is functioning as a telephone interface.
• the communication will be a series of pulses in the data signaling channel. This is made in a frame that consists of
• the microprocessor 35 for the preferred embodiment is the INTE 8748 available from Intel Corporation, Santa Clara, California.
• Figure 3 shows the microprocessor 35 interconnections.
• the control of the microprocessor 35 is accomplished by instructions.
• the instructions are written in terms of the particular mode of operation desired.
• the microprocessor thus has stored in its memory the programs and routines corresponding to each mode of operation.
• This routine disconnects the dial tone and resets the temporary register that stores the dailed digit to zero. Set the digit pointer to zero.
• This routine waits until the telephone receives the TOKEN to start transmitting.
• This TOKEN is the opportunity for the PC, board to start a transmission of information in the DATA SIGNALING CHANNEL.
• This routine goes to the channel free map and picks on empty channel. Then it sets the PLL to the selected channel frequency. This will be an ODD channel.
• This code will tell all the telephones in the sysem that this is a call.
• This reset of the frag set at step 13, will indicate that the telephone call has been placed.
• step 26 If 'REC IDR FLAG" set go to step 26.
• This routine checks if the other telephone or the truck has sent the Buzzy tone or ringing tone. If the IDR Flag is set it will go to a Local ring routine if no it will go to a buzzy tone.
• This routine is sent to "tell” to the whole sysem that the selected channels are not used anymore. This routine follows the steps below.
• the IDD Flag indicates that we receive a frame with an IDD code and my telephone number on it. This means that the telephone that I am calling on receives the ring, and the subscriber on the other end picks up his telephone and his unit sends me the IDD frame for me to stop my local ring.
• This step means that the sending telephone was hung up because the receiver did not answer and the sender decided to hang up.
• the function of this routine is explained in step 24.
• the microprocessor stays in this loop as long as the conversation goes on. Once the originator (my telephone) hangs up it jumps to the next step.
• the sender sends a frame with an IDS code, his number, my number and channel selected. With this information a channel opposite to his is selected. We will receive in an ODD channel and transmit. End.
• This frame is shown in Figure 5. This will activate the local ring at the send PC board.
• the send microprocessor will be executing steps 26 to 28.
• This frame will be sync byte, IDL code, my number, the caller number, channel number and check code.
• This Flag was set by my interrupt routine when we received it from the sender.
• WAIT UNTIL MY TELEPHONE (THE RECEIVER) IS ON HOOK.
• This Flag is a status request from another telephone to update its channel map. Normally the central office answers it. If not, any telephone could answer it after a Delay.
• the telephone with the TOKEN will answer after this delay, this provides the central office the opportunity to answer first.
• This routine is activated every time that a signal is received in the data signaling channel.
• the purpose of this routine is to receive the transmitting frame and:
• IDS Flag this indicates that a telephone is sending a calling signal. If this signal is received with my number I set the IDS Flag.
• This flag indicates that a telephone wants to know the voice channels free status map. . . REPLY FLAG
• This flag indicates that the signal being received is a bit string of the voice channel status. One bit per voice channel. One indicates free and zero indicates busy.
• WHAT I CLAIM IS l.A communications network which comprises: means to establish a data signaling channel in a coaxial cable; means to establish a plurality of voice channels separate from the data signaling channel in said cable; means to send a signal from a first source through the data signaling channel to a second source to determine if the second source is able to accept a signal transmission from the first source;

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• Engineering & Computer Science (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)

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• 1986
  • 1986-08-27 WO PCT/US1986/001780 patent/WO1987001541A1/en unknown
  • 1986-08-27 EP EP19860905589 patent/EP0243380A1/de active Pending
  • 1986-08-27 AU AU63728/86A patent/AU6372886A/en not_active Abandoned

Non-Patent Citations (1)

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