Multiple channel data communication system

Abstract

A multiple channel communications system and method for communication among multiple channels using a channel selectable MODEM. The system is comprised of a coaxial cable, a variety of interface units with attached communicating devices and a channel bridge. The interface units include a MODEM and a microprocessor based support element adapted for the attached communicating device. The channel bridge includes two or more .[.MODEM's.]. .Iadd.MODEMs .Iaddend.and a microprocessor based computer for receiving data from one MODEM and transmitting the data on another MODEM.

What is claimed is: 
     
       1. A data communication system comprising: a coaxial cable;   a plurality of .[.MODEM's.]. .Iadd.MODEMs .Iaddend.connected to the cable including means for selecting the transmit and receive .[.frequency bandwidths.]. .Iadd.frequencies .Iaddend.of each of the .[.MODEM's.]. .Iadd.MODEMs.Iaddend.;   means connected to the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.for supplying data to and receiving data from each of the .[.MODEM's.]. .Iadd.MODEMs.Iaddend.;   a central retransmission facility connected at the head end of the cable .[.whereby.]. .Iadd.such that .Iaddend.a signal transmitted by at least one of the .[.MODEM's.]. .Iadd.MODEMs .Iaddend.is received by the central retransmission facility and translated to the receive frequency .[.bandwidth.]. of the MODEM which transmitted said signal; and   a channel bridge connected to the cable including two or more .[.MODEM's.]. .Iadd.MODEMs .Iaddend.each of said .[.MODEM's.]. .Iadd.MODEMs .Iaddend.having different .[.transmit frequency bandwidths.]. .Iadd.transmitting frequencies .Iaddend.and different .[.receive frequency bandwidths.]. .Iadd.receiving frequencies than the other of said MODEMs in said channel bridge .Iaddend.and including means for transferring .[.a signal.]. .Iadd.signals .Iaddend.received by one of said MODEM's to another of said .[.MODEM's whereby the MODEM's.]. .Iadd.MODEMs in the channel bridge such that the MODEMs .Iaddend.connected to the cable which are transmitting and receiving .[.in.]. .Iadd.at .Iaddend.different .[.frequency bandwidths.]. .Iadd.frequencies .Iaddend.may receive signals from and transmit signals to each other .Iadd.via the channel bridge.Iaddend..   
     
     
       2. The data communication system of claim 1, wherein; the coaxial cable comprises a broadband coaxial cable.   
     
     
       3. The data communication system of claim 1, wherein.[.;.]..Iadd.:.Iaddend. the means connected to some of the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.for supplying data to and receiving data from the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.include means for supplying data to and receiving data from a terminal.   
     
     
       4. The data communication system of claim 1, wherein.[.;.]..Iadd.:.Iaddend. the means connected to some of the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.for supplying data to and receiving data from the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.include means for supplying data to and receiving data from a plurality of terminals.   
     
     
       5. The data communication system of claim 1, wherein.[.;.]..Iadd.:.Iaddend. the means connected to some of the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.for supplying data to and receiving data from the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.include means for supplying data to and receiving data from a host computer.   
     
     
       6. The data communication system of claim 1, wherein.[.;.]..Iadd.:.Iaddend. the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.include means for detecting the presence of a signal on the cable.   
     
     
       7. The data communication system of claim 1, wherein.[.;.]..Iadd.:.Iaddend. the means connected to the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.for supplying data to and receiving data from each of the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.includes means for comparing a plurality of the first bits of data received to the corresponding bits of data transmitted by one of the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.attempting to transmit a signal whereby data collisions may be detected.   
     
     
       8. The data communication system of claim 7, wherein; said means for comparing data are included in a universal synchronous receiver/transmitter.   
     
     
       9. The data communication system of claim 1, further comprising.[.;.]..Iadd.:.Iaddend. encryption means coupled with the means for supplying data to and from the .[.MODEM's.]. .Iadd.MODEMS .Iaddend.whereby data transmitted over the cable is encrypted by the transmission source and decrypted by the transmission destination.   
     
     
       10. The data communication sytem of claim 9, wherein; the encryption means includes an interchangeable encryption key.   
     
     
       11. The data communication system of claim 10, wherein; said encryption key comprises an erasable programmable read only memory.   
     
     
       12. The data communication system of claim 1, wherein.[.;.]..Iadd.:.Iaddend. said means for transferring a signal included in the channel bridge comprises.Iadd.: .Iaddend.a universal synchronous receiver/transmitter connected to said .[.MODEM's.]. .Iadd.MODEMS.Iaddend., data and address buses connected to each of said universal synchronous receiver/transmitters, a central processing unit connected to said data and address buses.Iadd., .Iaddend.and memory connected to said data and address buses.   
     
     
       13. A method of collision detection for data communication comprising the steps of: formating digital data by a transmitting node whereby a flag is inserted at the beginning of a transmission frame;   broadcasting said transmission frame onto a cable;   receiving said transmission frame by a central transmission facility;   translating said transmission frame by said central retransmission facility to a receive frequency bandwidth;   rebroadcasting said transmission frame in said receive frequency bandwidth onto said cable;   receiving said flag of said transmission frame by said transmitting node;   comparing said flag as received to said flag as transmitted to detect a collision of data;   aborting the broadcasting of said transmission frame when a collision of data is detected;   waiting a random time after detecting a collision of data; and   rebroadcasting said transmission frame after waiting a random time.