Patent ID: 6160990
Filing Date: 2000-12-12
Classification: H04N

Abstract:
A transmission path opening/closing device comprising:transmission path opening/closing means provided in at least one bidirectional transmission path of a cable network system for bidirectionally transmitting signals between at least one central equipment and at least one subscriber device via said bidirectional transmission path,said transmission path opening/closing means setting at least one upward transmission path of said bidirectional transmission path in a conductive state during a period when at least one upward signal transmitted from said subscriber device to said central equipment passes through said means, and setting said upward transmission path in a cutoff state during a remaining period;at lease one switch control section arranged corresponding to said subscriber device, andat least one gate switch section arranged in said bidirectional transmission path;said switch control section comprising at least one of means for detecting a transmission period of the upward signal from said subscriber device, and means for receiving notification information representing the transmission period of the upward signal generated by said subscriber device, and comprising means for generating a transmission indication signal representing the transmission period on the basis of a detection result of the transmission period or the received notification information, and sending the transmission indication signal to said bidirectional transmission path; andsaid gate switch section comprising means for setting said upward transmission path of said bidirectional transmission path in the conductive state during the period when the upward signal transmitted from said subscriber device passes through said gate switch section, and setting said upward transmission path in the cutoff state during the remaining period, in accordance with the transmission indication signal sent from said switch control section;wherein said switch control section sends a carrier having undergone spectrum spreading in accordance with a predetermined spread code sequence, as the transmission indication signal, andsaid gate switch section reversely spreads and reproduces the transmission indication signal, sent from said switch control section, in accordance with the predetermined spread code sequence to open/close the upward transmission path of said bidirectional transmission path in accordance with the reproduced transmission indication signal.