Lets try this Eric
The focuser being either the the standard model or the 10:1 model in which case the tiny gearing mechanism spins ten revolutions to one revolution to get movement in and out fast or slow.
Then the barlow is inserted to this focuser then the eyepiece is inserted into the barlow and then the whole shebang moves in unison ( in & out)
But remember Jen i tried to help you in a simple way .....
cheers Kev.