| Type | A-1520 | A-1521 | A-1520U | A-1521U | A-1571U | 
                  
                    | Interface | RS-232 TO RS-485
 | RS-232 TO RS-485/422/232
 | USB TO RS-485
 | USB TO RS-485/422/232
 | USB TO RS-485/422/232
 | 
                  
                    | Speed | Auto Tuner baud rate, 300~115200 bps | 
                  
                    | Transfer distance | Max. 1,200 m for speed 9.6 K bps; Max. 400 m for speed 115.2 K bps | 
                  
                    | Supports Max device | Maximum of 256 devices (Without repeater) | 
                  
                    | ESD Protection | Yes | 
                  
                    | Supply Voltage | 10~30VDC | -- | 
                  
                    | Power Consumption | Nearly 24V/0.5W | Nearly USB Port/0.5W | 
                  
                    | OS Driver |  | Windows 98 / ME / 2000 / XPWindow7(32/64 bit)/WinCE
 /Vista (32/64 bit) /Linux /Mac/Windows8(32/64 bit)
 | Windows 98 / ME / 2000 /XP/Window7(32/64bit)
 /WinCE/Vista (32/64 bit)
 /Linux /Mac /Windows
 Server 2008 R2/Android
 | 
                  
                    | Operation temperature
 | -20°C to +75 °C | 
                  
                    | Storage temperature | -25 °C to +80 °C | 
                  
                    | Installation | DIN-Rail or wall mounting | 
                  
                    | Connection | DB9(Female to RS-232)/USB(Type B); Removable 13-pin Terminal Block ( For RS-422 / 485 / 232 )
 |