This device works perfectly, it is installed to the remote entrance gate of fifteen meters from the house is old (late 19th century) and has thick rubble walls. Usually, only the wireless doorbells with insertable receiver works for me; but in this case, the two receivers (plug and battery) work and are a real asset to a good distribution of sound throughout the house and garden.
Only drawback, an error was made in the description on your site indicating a transmission range of 300 meters while the explanatory note mentions a range up to 200 meters.