RS323 through a USB port and my laptop

I'd used my laptop on another project as a dumb terminal and also to download stuff so I figured I'd use it on my Nicolet 1080. I'd written a simple echo program for the Nicolet. Took my laptop to the garage where the Nicolet was ( big 19 inch rack stuff ). I couldn't get it to work. On trying to initialize the com port, it came back as not initialize. I'm thinking, maybe it doesn't support 2400 baud or something. I bring in my other project that had been working in the front room and connect it up. It still isn't working??? Maybe I'd blown up the USB to serial dongle??? I had to take a break to do some chores around the house and, about 30 minutes later, it occurred to me what was wrong. The dongle runs from the USB power. The laptop doesn't provide the +5 when running on battery. I brought the power supply in to the garage and connected it up. All was working fine. So, for those using these dongles in the future, make sure they have a power source. It seems that not all laptops have the +5 when not powered from an external supply. 3 hours to learn something new. LOL Dwight