That Blue-colored audio port on the back of some PCs. It's called Line-in. It's for an aux cable. I'm using an old portable cassette tape player to listen to radio stations on my PCs speakers. 
That Blue-colored audio port on the back of some PCs. It's called Line-in. It's for an aux cable. I'm using an old portable cassette tape player to listen to radio stations on my PCs speakers.