answer:Crutchfield, a long-time car-audio vendor, offers suggestions on one of their forums filtered for the word “brake”. I didn’t understand your question until Googling around. It seems that some automotive DVD players require the parking brake to be set before they will work. In reality the player hooks up to a wire behind the dashboard that senses the parking brake and switches a voltage, acting as an enable / inhibit function. The tough part is installing such a wire if not already provided by the auto maker. But if there’s such a wire hooked up to your in-dash dvd, then the same wire should work just fine with any after-market dvd player with the same feature. Or you could probably fake it by electrically tying the dvd player’s parking brake input voltage to either +12 volts or ground (possibly through a resistor), the details of which would be in the player’s installation / service manual. Google the make & model along with the word “brake”, which doesn’t mean much else in this context.