版权法所豁免的合理使用范围很窄，在此范围内，侵权者未经许可使用他人作品是不负有赔偿责任的。
Fair use is a very narrow exemption under copyright law where an infringer is not liable for using someone else's copyrighted work without permission.
这是因为有保护许可的数据库通常对使用范围由严格限制，像图书馆大楼或校园内的IP范围才可使用。
This is because licensed databases are often restricted to a particular location by Internet Protocol (IP) ranges like the library building or university campuses.
在全球定位系统信号不可见的情况下，可使用伪卫星系统扩展其使用范围，全球定位系统信号发生器是其中的关键组成设备。
GPS pseudolites systems were employed to extend the availability of GPS when satellites signals were not seen. GPS signal generators were the core part of pseudolites system.
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