Aux cable behind radio?

[Difflay]

Okay so when I put in my aftermarket deck into my car I noticed that the antenna plug has a weird box on the antenna wire and it goes in to two more wires on goes in towards the glove box and one goes down behind the center console and has like 3 feet of wire that goes to an auxiliary cord but the jack is really small not like a normal headphone jack. What is it? There's no auxiliary on the stock deck and it doesn't seem to do anything... Sorry if the description sucks it's hard to explain lol

[Cliff8928]

FM modulator?

[Difflay]

Yup that's what It is! Thanks I was so confused why it was there

[Nas Escobar]

That sounds like it's an old school radio. But that will be a FM modulator.