Time slot arrangements for local area network systems
First Claim
1. A communication system comprising:
- a common communication medium being arranged to carry information on a time division multiplex basis in which each time slot includes an active period for the transmission of a burst of information signals and a transit period, the communication medium having no master clocking arrangement;
a plurality of subscribers interface units each connected to the common communication medium, each interface unit includes;
a data transmission arrangement for transmitting information signals on to the communication medium;
a data reception arrangement for receiving information signals from the communication medium;
an internal timing means arranged to produce timing signals on a time division multiplex basis with each time slot including said active period and said transit period with a time slot marker at the midpoint of the transit period of each internal time slot;
means for monitoring the timing of traffic data bursts on the communication medium and generating a time slot marker relevant to the communication medium time slot for detecting a predetermined descrepancy between the transit period produced by said internal timing means and the transit period of each of the time slots on the communication medium; and
means for adjusting the internal timing means within each interface unit responsive to said means for monitoring so that the time slot timing cycle within the interface unit corresponds with that of the data signals on the communication medium.
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Accused Products
Abstract
In local area networks (LAN'"'"'s) which are required to operate in duplex mode it is necessary for the common communication medium to be operated in a t.d.m. manner. Because the LAN has no common equipment, every station is arranged to contain its own control circuitry and crystal controlled clocking system to produce time slot markers. The system is organized so that each time slot comprises an active period for data or speech transmission or contention resolution, followed by a transit period in which the data or speech reaches the destination. Ideally time slot markers occur simultaneously in both stations and for intermediate stations there is a tolerance which reaches a maximum at the midway point of the network communication medium. The multiplexing system arranges that the time slots are packed as closely together as the delay between most separated stations will allow. The near simultaneous occurrance of time slot markers is maintained by all stations whether busy or free by observing the timing of traffic on the communication medium and adjusting the timing of the station time slot marker to occur in the time between data or speech bursts of existing traffic.
33 Citations
13 Claims
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1. A communication system comprising:
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a common communication medium being arranged to carry information on a time division multiplex basis in which each time slot includes an active period for the transmission of a burst of information signals and a transit period, the communication medium having no master clocking arrangement; a plurality of subscribers interface units each connected to the common communication medium, each interface unit includes; a data transmission arrangement for transmitting information signals on to the communication medium; a data reception arrangement for receiving information signals from the communication medium; an internal timing means arranged to produce timing signals on a time division multiplex basis with each time slot including said active period and said transit period with a time slot marker at the midpoint of the transit period of each internal time slot; means for monitoring the timing of traffic data bursts on the communication medium and generating a time slot marker relevant to the communication medium time slot for detecting a predetermined descrepancy between the transit period produced by said internal timing means and the transit period of each of the time slots on the communication medium; and means for adjusting the internal timing means within each interface unit responsive to said means for monitoring so that the time slot timing cycle within the interface unit corresponds with that of the data signals on the communication medium. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification