USB 2.0 provides for a maximum cable length of 5 meters for devices running at Hi Speed (480 Mbit/s). The primary reason for this limit is the maximum allowed round-trip delay of about 1.5 μs. If USB host commands are unanswered by the USB device within the allowed time, the host considers the command lost. When adding USB device response time, delays from the maximum number of hubs added to the delays from connecting cables, the maximum acceptable delay per cable amounts to 26 ns.The USB 2.0 specification requires that cable delay be less than 5.2 ns per meter (192 000 km/s, which is close to the maximum achievable transmission speed for standard copper wire).
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In terms of production enterprises, it is necessary to comply with the regulations for rare earth industries, industrial policies, and management of rare earth industries. The quality of products meets the current national standards and ISO9000 quality system certification is obtained.
The rare earth raw materials of the production enterprises must be from mining qualified rare earth mining enterprises of the Ministry of Land and Resources, and have environmental protection facilities (including on-line monitoring facilities) that are compatible with the scale of production, and the discharge of pollutants meet the national or local pollutant discharge standards. .
According to the announcement, the circulation enterprises applying for rare earth export quotas must obtain ISO9000 quality system certification.
In addition, the announcement stated that in order to increase the concentration of business operations and reduce the number of exporting companies, companies registered after January 1, 2007, whose rare earth export performance among their affiliates or associated companies will not be identified.
The announcement stressed that in order to further regulate the export of rare earths, the state will exercise strict supervision over rare earth export enterprises. Any enterprise that appears in the course of the implementation of quotas during the implementation of various types of illegal activities, and does not implement national industrial or resource environmental protection policies will, upon verification, recover its rare earth export quotas for the year and suspend until the cancellation of its current annual export quota application qualifications.
In addition, the Ministry of Commerce also announced the conditions and procedures for the application of export quotas for coke and phosphate rock in 2011, as well as the state-owned export enterprises of tungsten, bismuth, and silver, and the eligibility criteria and reporting procedures for export suppliers of tungsten and antimony.
Rare Earth Export Quota Declaration Launched in 2011
The Ministry of Commerce issued an announcement on the 11th, announcing the application conditions and reporting procedures for rare earth export quotas in 2011. Enterprises that have obtained rare earth export quotas in 2010 can apply for 2011 rare earth export quotas in accordance with relevant standards set out in the announcement.