Communications systems

Claim 1

A method of controlling a communications network comprising a plurality of stations which can communicate via a closed communication loop; said method including: providing information in digital form for transmission from one station to another in message blocks which circulate around the loop, each message block being provided as a first group of control bits and a second group of data bits, controlling each of said plurality of stations having data to transmit to assume an active state in which it inserts digitally encoded information into empty message blocks for transmission to a destination station via the loop, causing any of said stations in an active state, if it has inserted information into d message blocks, where d is an integer greater than zero and is variable, to enter a state in which it cannot gain access to empty blocks for the transmission of information until it is reset, controlling any receiving station after receiving data from a message block to set the control bits of said message block to indicate a further allocation request; controlling the receiving station setting the control bits of said block to further modify said control bits upon the station recognizing that said block has traveled unmodified once around the loop, said control bits being modified to indicate a reset; said resets being issued to each of said stations so that no station is in a preferential position with regard to the rate of reception of resets.

Claim 2

A method of controlling a communications network comprising a plurality of stations which can communicate via a closed communication loop; said method including: providing information in digital form for transmission from one station to another in message blocks which circulate around the loop, each message block being provided as a first group of control bits and a second group of data bits, controlling each of said plurality of stations having data to transmit to assume an active state in which it inserts digitally encoded information into empty message blocks for transmission to a destination station via the loop, causing any of said stations in an active state, if it has inserted information into d message blocks, where d is an integer greater than zero and is variable, to enter a state in which it cannot gain access to empty blocks for the transmission of information until it is reset, controlling any receiving station after receiving data from a message block to set the control bits of said message block to indicate a further allocation request; controlling the receiving station setting the control bits of said block to further modify said control bits upon the station recognizing that said block has traveled unmodified once around the loop, said control bits being modified to indicate a reset; said resets being issued to each of said stations so that no station is in a preferential position with regard to the rate of reception of resets.

Claim 10

A system as claimed in any one of claims 5 or 6, wherein a station downstream of a station initiating a further allocation procedure has control means capable of modifying control data in an emptied block to indicate a full block and to insert message data therein so as to terminate the further allocation procedure.

Claim 11

A system as claim in any one of claims 5 or 6 wherein detection means are provided to prevent allocation of a station which itself is concurrently carrying out a further allocation procedure in which some but not all stations have already received a further allocation.

Claim 12

A system as claimed in any one of claims 5 or 7, wherein modifying means are provided to adjust the allocation of d message block dependent on message block usage.

Claim 13

A system as claimed in any one of claims 5 or 6, wherein priority allocating means are provided to identify delay sensitive or non-delay sensitive messages.

Claim 14

A system as claimed in any one of claims 5 or 6 including means for determining whether message sources which may additionally be connected to any station and requiring additional message blocks can be handled by the station without system overload.

Claim 15

A system as claimed in any one of claims 5 or 6, including means for handling synchronous and asynchronous message packets for the message blocks.

Claim 16

A method of operating a communication system including a plurality of stations comprising: allocating d message blocks only to each of said plurality of stations within the system to avoid monopolisation by any station, where d is an integer greater than zero and is variable; utilizing an emptying block being emptied at any station for the purpose of testing the allocation availability of further message blocks regardless of whether the d allocation has been exhausted; and allocation further message blocks whenever the utilised block has travelled from said any station to all other stations in said communication system and back to the station where it was emptied without being modified by another station.

Claim 17

A method of operating a communication system including a plurality of stations comprising: allocating d message blocks only to each of said plurality of stations within the system to avoid monopolisation by any station, where d is an integer greater than zero and is variable; utilizing an emptying block being emptied at any station for the purpose of testing the allocation availability of further message blocks regardless of whether the d allocation has been exhausted; and allocation further message blocks whenever the utilised block has travelled from said any station to all other stations in said communication system and back to the station where it was emptied without being modified by another station.