UPDATE after 5 weeks:
1. has worked well until a few days ago an error occurred since. The unit can only be controlled in Master Mode other devices if they are set to TTL mode. Furthermore, in the Master mode, the device will not work on TTL. Whether the latter from the beginning was so I do not know. I have searched everywhere but no detailed operating instructions found.
The fact is that the device is not working as stated in the description.
2. Seller does not respond to request