A question for you that understand electronics. I dabble, but don't have depth of knowledge in it so I need the collective wisdom of the list. If you have a splitter, or a "Y", with one male jack and two female jacks - this would allow you to plug the one male jack into the 'voice out' line of a device (let's say an FM radio) and into the two female jacks of the splitter you plug in two listening devices (let's say two sets of earbuds). That FM radio signal could be heard by two listeners at the same time. Now, if you unplugged one set of those earbuds and plugged in your gps 'voice out' line into the female jack previously occupied by that one set of earbuds, would the listener on the remaining earbud set still plugged in be able to hear the gps device's voice give directions if the FM radio was silenced or off? Or do splitters come with diodes built-in that restrict direction of current and thus allow only the FM radio signal to travel to the earbuds? Thus, is the male jack for signal into the splitter and female jacks for signal out of the splitter only, or can the current flow be reversed?