I thought it worked like a gauge By hookin up like a gauge and then running to the deck Maybe i wrong just really cool looking and wanted to get it looks clean
i've got the premier deh-p800prs and it's got it built in. it seems to be pretty accurate, about 11.8 when the car is in acc and about 14.4 to 14.6 when the car is on. i'd assume the premier deh-p880prs also has it seeing it's almost the same unit. i'm sure some of the others have it as well. if the question was already answered, i'm sure you can find it somewhere on the forum.