Three Versatile Powering Options Model 485BAT3 features power versatility, making it perfect for field testing solutions. It can be powered in three ways: batteries, port powered, or external power supply (not included, sold separately). Use the battery power option with a low power RS-232 port (found on many laptops) or no handshake lines or when it is inconvenient to use a power supply. Model 485BAT3 will draw as much power as possible from the RS-232 port and get any additional current necessary from the batteries. If you have a full power-port and all your handshake lines, turn off the battery switch. This allows you to run full port-powering and saves the batteries for emergencies. Note: The battery On/Off switch conserves battery life. It does not turn on and off all power to the unit. Lastly, a stripped and tinned 12VDC external power supply may be used. Simply attach it to the terminal blocks and plug it in. Model 485BAT3 converts unbalanced RS-232 signals to balanced RS-422 or RS-485 signals. RS-485 is an enhanced version of the RS-422 standard, allowing multiple drivers and receivers on a 2-wire system.