toyota 2702 EC1 series forgotten what the dials are for?

Hi I own the above machine i have not used it for several years
threading up etc all comes as automatic to me but i have totally forgotten what the top and bottom dials on this machine do.
i really dont want to have to spend £10 on a manual just to find out! i have experimented and for the life of me can not see what it is doing probably because i am setting it wrong so straight stitch only for me. I just use straight and diagonal, i quickly learned at 14 that all the other cams with the machine were pointless.