[Repeater-Builder] remote head ?

[David]

Hi Everyone, i have a remote head fm828/25 A/R MK2 radio with a remote
head that i hope to use as a repeater there are two sockets on the back of the 
radio one has a red strip around it what socket do i plug the remote head into 
to see if the radio work's  ??...Rgs David  VK4DJC.