1-2 Appearance and Names of Parts 1-2 Appearance and Names of Parts 1 When the product is unpacked, it appears as below. (Example of 3G3RX-A2150/A4150 to A2220/ A4220) Overview Front cover Digital Operator Spacer cover Terminal block cover Open the terminal block cover and you can connect cables to the main circuit terminal block, as well as the control circuit terminal block. Also, open the front cover and you can mount the optional board. 1-4 Position for installing optional board 1 Position for installing optional board 2 Control circuit terminal block Main circuit terminal block Backing plate