Digital signal transmission system
First Claim
1. In a digital signal transmission system having a plurality of individual stations coupled to a communications cable via taps, said stations transmitting time-division multiplexed digital signals on said communications cable with fixed time positions being assigned to said signals within periodically repeated time base frames, said frames being subjected to further divisions so that individual ones of said stations transmit packets which occupy specific time periods in said frame, some of said signals being from stations operating in a first mode, in which collisions between data packets transmitted from different stations are detected and the transmitting stations retry transmission after waiting a predetermined interval, and others of said signals being from stations operating in a second mode, in which collisions between data packets transmitted from different stations are detected and the transmitting stations retry transmission according to whether or not a carrier is present, the improvement comprising:
- in said stations operating in said second mode, send logic circuit means for preventing stopping of digital signal transmission from a station even if a collision occurs with a signal transmitted from said station in said first mode; and
receive logic circuit means for preventing stopping of digital signal reception even if a collision is detected after start of digital signal reception.
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Accused Products
Abstract
A digital signal transmission system for communicating digital signals in both a Faxnet and a CSMA/CD mode over a single cable. The system includes plural stations coupled to the single cable via taps, the stations transmitting time-division multiplexed digital signals on the cable with fixed time positions assigned to the signals within periodically repeated time base frames, which frames are subjected to further divisions so that individual ones of the stations transmit packets which occupy specific time periods in the frame. A send logic circuit prevents stopping of digital signal transmission from a station even if a collision occurs with a signal transmitted from the station in the CSMA/CD mode while a receive logic circuit prevents stopping of digital signal reception even if a collision is detected after start of digital signal reception.
26 Citations
11 Claims
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1. In a digital signal transmission system having a plurality of individual stations coupled to a communications cable via taps, said stations transmitting time-division multiplexed digital signals on said communications cable with fixed time positions being assigned to said signals within periodically repeated time base frames, said frames being subjected to further divisions so that individual ones of said stations transmit packets which occupy specific time periods in said frame, some of said signals being from stations operating in a first mode, in which collisions between data packets transmitted from different stations are detected and the transmitting stations retry transmission after waiting a predetermined interval, and others of said signals being from stations operating in a second mode, in which collisions between data packets transmitted from different stations are detected and the transmitting stations retry transmission according to whether or not a carrier is present, the improvement comprising:
- in said stations operating in said second mode, send logic circuit means for preventing stopping of digital signal transmission from a station even if a collision occurs with a signal transmitted from said station in said first mode; and
receive logic circuit means for preventing stopping of digital signal reception even if a collision is detected after start of digital signal reception. - View Dependent Claims (2, 3, 4)
- in said stations operating in said second mode, send logic circuit means for preventing stopping of digital signal transmission from a station even if a collision occurs with a signal transmitted from said station in said first mode; and
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5. In a digital signal transmission system having a plurality of individual stations coupled to a communications cable via taps, said stations transmitting time-division multiplexed digital signals on said communications cable with fixed time positions being assigned to said signals within periodically repeated time base frames, said frames being subjected to further divisions so that individual ones of said stations transmit packets which occupy specific time periods in said frame, some of said signals being from stations operating in a first mode, in which collisions between data packets transmitted from different stations are detected and the transmitting stations retry transmission after waiting a predetermined interval, and others of said signals being from stations operating in a second mode, in which collisions between data packets transmitted from different stations are detected and the transmitting stations retry transmission according to whether or not a carrier is present, the improvement comprising:
- in said stations operating in said second mode, means for transmitting a dummy signal of a specific length by a station which is about to complete transmission of signals, said dummy signal being directed to a position in a time period which is sequentially assigned to said station in a frame next to a last digital signal which said station has transmitted, thereby informing all other stations that said station is ending use of a time period which it has been occupying.
- View Dependent Claims (6, 7, 8, 9, 10, 11)
Specification