The devices that plug into the cigarette lighter and play sound from a USB drive through car radio speakers have the ability to remember where they left off, and, even when power is removed from them when the car is turned off, they restart from the start of the file or segment, often the start of a song, that had been playing when the car was turned off.
My question is, How does the device keep track of where to start up again. Is there a file written to the device that plugs into the cigarette lighter, or is it written to the USB drive? If to the device itself, will it look for a specific file name if a different USB drive is plugged in, or can it be fooled then into trying to play song 6, for example, on a different usb drive.
I could experiment to learn this stuff but I just don't have any time to do that before or during my upcoming car trip, and you might already know. Plus I wanted to tell you how great these things are if your car radio doesn't have a USB or 3.5mm input. See background.
Similar question about MP3 players. If one inputs to the car radio via the 3.5mm jack, it seems that the intermediate device can't keep track of anything, but the mp3 player can. Obviously, the information is stored in the MP3 player, but without my having to test, does anyone know if separate positions are kept for "music", "ebooks", and "podcasts"?. If so, that provides some versatility, and I could for example, put popular music in music, classical music in ebooks and broadway shows in podcasts. Or science podcasts in ebooks and history podcasts in podcasts.
Background: My 2005 Toyota seems to have been made just a year or two before it would have been possible to connect USB and 3.5mm inputs to its radio, using the CD changer or satellite port.
I wanted that because in that case the steering wheel controls would likely have controlled what was playing on a USB drive, and the song information would have displayed on the radio.
But since I couldn't have that, it turns out, except for the quality of the microphone (which might reflect more the acoustics of the car. The sound from the microphone is very intelligible, but my friend whom I called is good at being critical) the devices that plug into a cigarette lighter and communicate with RF do an amazing job. And they cost only about 16 to 22 dollars. One very compact one is only 11. I can give you specific urls if you want, but much of the difference is what will work best physically in your own car, depending on where the lighter is and what direction the opening points.
Other differences are whether they have a USB input, a USB charging port, a 3.5mm input, a TF input, a 1" square screen or less, and whether they will also connect with bluetooth to your cell phone. If they do the latter, they have a button that will answer the phone and hang up, and they use their own built-in microphone and the car radio speakers.