Abstract A system for the transmission of data packets of mutually equal durations from a plurality of substations to a main station via one or more transmission channels, the main station comprising transmission means for transmitting on each transmission channel a synchronising signal which indicates the beginning of a frame, programmable memory means for storing, in respect of each transmission channel, a maximum link establishment time and a maximum link disestablishment time both of which being a characteristic of the transmission channel from the substations to the main station, the substations each comprising programmable memory means for storing said maximum link establishment times and said maximum link disestablishment times, means which on reception of the synchronising signal on a transmission channel subdivide the frame into a number of consecutive time slots of mutually equal durations at least equal to the sum of the duration of a said data packet, said stored maximum link establishment time and said stored maximum link disestablishment time of that transmission channel, means for transmitting a said data packet, if so desired, by selecting a time slot from the sequence of time slots and transmitting the data packet within a period within the selected time slot, the period beginning at a time equivalent to said stored maximum link establishment time of that transmission channel after the beginning of the selected time slot and ending at a time equivalent to said stored maximum link disestablishment time of that transmission channel before the end of the selected time slot.
A system for the transmission of data packets of mutually equal durations from a plurality of substations to a main station via one or more transmission channels, the main station comprising transmission means for transmitting on each transmission channel a synchronising signal which indicates the beginning of a frame, programmable memory means for storing, in respect of each transmission channel, a maximum link establishment time and a maximum link disestablishment time both of which being a characteristic of the transmission channel from the substations to the main station, the substations each comprising programmable memory means for storing said maximum link establishment times and said maximum link disestablishment times, means which on reception of the synchronising signal on a transmission channel subdivide the frame into a number of consecutive time slots of mutually equal durations at least equal to the sum of the duration of a said data packet, said stored maximum link establishment time and said stored maximum link disestablishment time of that transmission channel, means for transmitting a said data packet, if so desired, by selecting a time slot from the sequence of time slots and transmitting the data packet within a period within the selected time slot, the period beginning at a time equivalent to said stored maximum link establishment time of that transmission channel after the beginning of the selected time slot and ending at a time equivalent to said stored maximum link disestablishment time of that transmission channel before the end of the selected time slot.
Claim 2
Dependent Claim
33 words
A system as claimed in claim 1, wherein the system comprises an infrastructure for one or more of the transmission channels for transmitting data via the infrastructure between the main station and substations.
Claim 3
Dependent Claim
28 words
A system as claimed in claim 2, wherein the system comprises one or more repeaters on one or more said transmission channels for retransmission of said data packets.
Claim 4
Dependent Claim
56 words
A system as claimed in claim 1,2 or 3, wherein the main station and substations each have means for changing the stored maximum link establishment times and maximum link disestablishment times in their respective programmable memory means, in response to changes in the maximum link establishment times and maximum link disestablishment times of the transmission channels.
Claim 5
Independent Claim
109 words
A system as claimed in any one of the preceding claims, wherein the transmission channels are simplex channels, and the main station had stored in the programmable memory means further link disestablishment times and link disestablishment timed of respective transmission channels each being a characteristic of their respective transmission channels from the main station to the substation and the substations have stored in their programmable memory means said further link establishment and disestablishment times and the said means of the substations subdivide the frame such that the first time slot begins at a time equivalent to the stored further link disestablishment time after the beginning of the synchronising period.
Claim 6
Independent Claim
18 words
A system for transmitting data packets, the system being substantially as described with reference to the accompanying drawings.
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