Multiple access bus communications system

Claim 2

A multiple access bus communications system comprising: a communications bus including a pair of oppositely-directed unidirectional signal paths connecting a plurality of remote locations, and a path coupling means for transferring signals from the inbound path to the outbound path at one end of said pair of paths, a plurality of bus interface units (BIU's), each one of said BIU's being coupled to said bus at an associated one of said remote locations, and including: A. means for identifying times when no carrier signal is present on said outbound path, B. means for selectively transmitting modulated carrier signals on said inbound path, wherein the carrier modulation for each of said modulated carrier signals is representative of a data packet, said transmitting means being operative to commence a modulated signal carrier transmission only during said identified times, C. means for receiving modulated carrier signals from said outbound path, D. means for monitoring said received modulated carrier signals, said monitoring means being operative during a collision window, said collision window, commencing at least as early as tl from the time when said transmitter means initiates a transmission on said inbound path, and extending until at least t 2 after said transmission initiation time, where t 1 equals the signal propagation time along said inbound path, said path coupling means, and said outbound path from the location of said one BIU back to said one BIU and t 2 equals the signal propagation time along said inbound path, said path coupling means, and said outbound path from the location of the BIU farthest from said path coupling means back to the location of said one BIU, E. transmitter control means responsive to said monitoring means for disabling said transmitting means immediately when at least a portion of said monitored signals fail to correspond to a corresponding portion of the modulated carrier signal of said transmission, and for disabling said transmitting means following the complete transmission of said modulated carrier signal otherwise.

Claim 3

A system according to claim 1 wherein each of said EIU's has an associated address and said data packet includes data representative of the address of the BIU intended to receive said packet, and wherein said receiving means of at least one BIU further includes means for identifying and storing data signals representative of the modulation on said received modulated carrier signals including a portion corresponding to the address of said one BIU.

Claim 5

A system according to claim 1 wherein said transmitting means is operative to again commence a modulated signal carrier transmission following detection of a signal correspondence failure by said transmitter control means at a time delaved from the previous transmission time of said modulated carrier signal by a random interval.

Claim 6

A multiple access bus communications system comprising: a communications bus including a pair of oppositely-directed, unidirectional signal paths connecting a plurality of remote locations, and a path coupling means for transferring signals from the inbound path to che outbound path at one end of said pair of paths, a plurality of bus interface units (BIU's), each one of said BIU's being coupled to said bus at an associated one of said remote locations, and including: A. bus activity monitor means for identifying times when no carrier signal is present on said outbound path, B. transmitter control means, C. transmitter means responsive to said transmitter control means, said transmitter means including means for transmitting a modulated carrier signal on said inbound path, wherein said carrier modulation for each of said modulated carrier signals is representative of a data packet, said packet including a header portion having at least a portion representative of an address word associated with its location of the transmitting BIU and at least a portion representative of an address word associated with the location of the BIU intended to receive said packet, said portions together having a duration at least equal to the signal propagation tine along said inbound path, along said path coupling means, and along said outbound path from the location of the BIU farthest from said path coupling means back to said farthest BIU, D. receiver means for receiving modulated carrier signals on said outbound path and for detecting the modulation of said carrier, E. collision detection means operative during a collision window to compare said detected modulation with said packet header portion representative of the transmitting and intended receiver BIU's address words, said transmitter control means being operative to activate said transmitter means only during said identified times, and being responsive to said collision detection means to disable said transmitter means following reception of said packet in its entirety by said receiver means when said detected modulation and said packet header portion match, and to disable said transmitter means immediately when said detected modulation and said packet portion fail to match, said collision window commencing at least as early as t l from the time when said transmitter means initiates transmission on said inbound path, and extending until at least t 2 after said transmission initiation time, where t 1 equals the signal propagation time along said inbound path, said path coupling means, and said outbound path from the location of said one BIU back to said one BIU, and t 2 equals the signal propagation time along said inbound path, said path coupling means, and said outbound path from the location of the BIU farthest from said path coupling means back to the location of said one BIU.

Claim 7

A multiple access bus communications system comprising: a communications bus including a pair of oppositely-directed, unidirectional signal paths connecting a plurality of remote locations, and a path coupling means for transferring signals from the inbound path to che outbound path at one end of said pair of paths, a plurality of bus interface units (BIU's), each one of said BIU's being coupled to said bus at an associated one of said remote locations, and including: A. bus activity monitor means for identifying times when no carrier signal is present on said outbound path, B. transmitter control means, C. transmitter means responsive to said transmitter control means, said transmitter means including means for transmitting a modulated carrier signal on said inbound path, wherein said carrier modulation for each of said modulated carrier signals is representative of a data packet, said packet including a header portion having at least a portion representative of an address word associated with its location of the transmitting BIU and at least a portion representative of an address word associated with the location of the BIU intended to receive said packet, said portions together having a duration at least equal to the signal propagation tine along said inbound path, along said path coupling means, and along said outbound path from the location of the BIU farthest from said path coupling means back to said farthest BIU, D. receiver means for receiving modulated carrier signals on said outbound path and for detecting the modulation of said carrier, E. collision detection means operative during a collision window to compare said detected modulation with said packet header portion representative of the transmitting and intended receiver BIU's address words, said transmitter control means being operative to activate said transmitter means only during said identified times, and being responsive to said collision detection means to disable said transmitter means following reception of said packet in its entirety by said receiver means when said detected modulation and said packet header portion match, and to disable said transmitter means immediately when said detected modulation and said packet portion fail to match, said collision window commencing at least as early as t l from the time when said transmitter means initiates transmission on said inbound path, and extending until at least t 2 after said transmission initiation time, where t 1 equals the signal propagation time along said inbound path, said path coupling means, and said outbound path from the location of said one BIU back to said one BIU, and t 2 equals the signal propagation time along said inbound path, said path coupling means, and said outbound path from the location of the BIU farthest from said path coupling means back to the location of said one BIU.

Claim 8

A system according to claim 5 further comprising: F. packet receiver means to identify said detected modulation as a received packet when said detected modulation includes a header portion representative of said address word associated with its location.

Claim 9

A system according to claim 5 wherein transmitter control means is operative following detection of a match failure to activate said transmitter means to again transmit a modulated carrier signal at a time delayed from the previous transmission time for said modulated carrier signal by a random interval.