4 sets in maximum at the same place.
a. The distance between two base stations is at least 1.5 meters when multiple Solidcom M1 systems are working together.
b. You are advised to install the base station in an open place higher than 1.7 meters. A confined environment may affect the wireless signal quality and reduce the transmission range.
The firmware requirements: later V 220.127.116.11 .
Firmware upgrade manual:https://drive.google.com/file/d/1WXzd6_gsRUciGxzqtk0laD8ju2u61sw-/view?usp=sharing