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US 4,398,288 AGranted
Loop type data highway system for data transmission
AssigneeHitachi, Ltd.
InventorsSadao Mizokawa, Seiichi Yasumoto, Masahiro Takahashi
Life of this patent
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Abstract
The periodicity of an input signal is monitored by means of a re-triggerable one-shot multivibrator. When an input signal interruption is detected by the output of the multivibrator, the state of the input signal interruption is held to interrupt the transmission until a phase locked loop is demodulated. The transmission is not opened until the phase locked loop is brought into its synchronous state.
Claims4
A looped highway system for data transmission, comprising:
- a plurality of stations connected in series through a common bus to form a closed loop, in which data transmission between apparatus connected with said stations is carried out through the corresponding stations, wherein each of said stations includes a receiver and a transmitter;
- wherein one of said stations includes means for generating a clock signal, while the remaining stations include means having a phase locked loop for deriving the clock signal out of the data which has been received through the receiver therein;
- each of said remaining stations including first monitor means for detecting that the data received through the receiver thereof has lost a predetermined periodicity, and second monitor means for detecting that said phase locked loop is at its synchronous state, and control means responsive to the output of said first monitor means for interrupting the feed of the data therefrom to the adjoining station from the transmitter thereof for a predetermined time period and for allowing the feed of data to said highway on condition that said predetermined time period has elapsed and that said second monitor means provides an output indicating that said phase locked loop is at its synchronous state.
Dependencies are inferred from the claim text.