SL502 BYPASS EQ / NO AUDIO ?

[EmptyMusicBox1]

hello

I have rack SL502 in 1u RACK work perfectly, But when i use the "IN" switch the audio CUT !! i want use the switch as a Bypass EQ only , no cut audio

i use the unblanced input 31c and the unbalanced output 29c

i read exist a I/O  EQ/DYNAMICS BUS it's a solution ?

thanks for your Help