Excellent! Purchased due to covid 19 and installed in a courtroom to notify the secretary by both the public and lawyers. With a press of the button, it rings loudly twice. The good thing is that there doesn't need to be visual contact between the transmitter and the receiver, as it can penetrate through walls.

The only negative thing is the user manual. It is a small booklet in Chinese. Since it is sold outside of China, it should have been written at least in English.

Just received it. Tested it at 100m without line of sight and it communicates normally. It probably covers even greater distances.

The basic manual is only in Chinese (not even in English). I hope it proves reliable over time