WM21 is a 4G Modem designed to provide cat M or cat NB access to the RS232 equipment. It comes with 1 RS232 port, 1 USB Type-C port, 1 Sim Slot and 1 Cellular Antenna interface. WM21 supports both RS232 communication and power supply via an ethernet cable. With delicate design, WM21 is especially applicable to the metering industry.