Samsung UN75ES9000F E-Manual page 222

(analog channels only) The analog
caption function operates in either
analog TV channel mode or when a
signal is supplied from an external
device to the TV. (Depending on the
broadcasting signal, the analog caption
function may or may not work with
digital channels.)
Default / Service1 – Service6 / CC1 –
CC4 / Text1 – Text4: (Digital channels
only) The digital caption function