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US 5,184,121 AGranted
Field sensor communication method and system
AssigneeHitachi, Ltd.
InventorsMakoto Kogure, Akira Sase, Masao Fukunaga
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AssigneeHitachi, Ltd.
InventorsMakoto Kogure, Akira Sase, Masao Fukunaga
Estimating the term…
In a communication system in which a plurality of communication units are connected to a common two-wire transmission line and signal transmission/reception is made between the communication unit and a field sensor connected to one end of the transmission line, the communication unit transmits a signal to the field sensor under the condition that no signal is present on the transmission line during a period of time not shorter than a predetermined time while the field sensor transmits a signal indicative of in-use of the transmission line at an interval of time shorter than the predetermined time during a period of time until the field sensor sends back a signal in response to the signal from the communication unit, whereby signal collision between the plurality of communication units is prevented with no provision of any specific means.
A field sensor communication method for a communication system comprising a field sensor for detecting a physical quantity of a process and a communication unit, either said field sensor or said communication unit transmitting or receiving a transmission signal through a signal transmission line, the method comprising the steps of:
A field sensor communication method for a communication system comprising a field sensor for detecting a physical quantity of a process and a communication unit, either said field sensor or said communication unit transmitting or receiving a transmission signal through a signal transmission line, said method comprising the steps of:
A field sensor communication method for a communication system comprising an industrial instrument and a communication unit, said industrial instrument transmitting to or receiving from said communication unit a transmission signal through a signal transmission line, said method comprising the steps of:
A field sensor communication system comprising a field sensor for detecting a physical quantity of a process and a communication unit, either said field sensor or communication unit transmitting or receiving a transmission signal through a signal transmission line, either said field sensor or said communication unit including a transmitting side including means for detecting an absence of said transmission signal on said signal transmission line during a first period of time which is not shorter than a predetermined time period and to transmit a first signal after said first period of time, and the other of either said field sensor or said communication unit including a receiving side including means for transmitting a second signal indicative of in-use of said signal transmission line during an interval of time shorter than said predetermined time period after said first signal is received by said receiving side and until a response signal is transmitted by said receiving side.
Dependencies are inferred from the claim text.