Kr-950

Hi,I recently owned a Kenwood KR-950B Receivier, it`s actually not bad,it sounds very well with my speakers.(some older Noname speakers) The question I have is: there is an In- and Output(l&r) at the back writed on with "ADP". Has anyone an Idea for what it is? maybe a split after the preamp?

greetings
BastiB