If a patent is exploited without the permission of the patentee, that is, the patent right is infringed and disputes are caused, the parties concerned shall negotiate and issue a warning letter of infringement. If negotiation fails, a lawsuit may be brought to the people's court or the competent department of the relevant personnel may be requested to handle it.
Warning letter is a right given by law to the obligee to resolve disputes through self-help. Its users are not limited to manufacturers and sellers, but also traders of manufacturers such as importers and users. However, for different objects, the obligee's duty of care when using the "warning letter" is completely different.