optical-coax converter help

[stow123]

my reciever has optical out and only coax as an input i think its coax anyway as its green.and ps3 is optical out too so gonna need a converter ,do i just get the opposite to what ive got so optical in and coax out converter box? also is it still gonna be digital sound and will it still carry dts 5.1 and DD 5.1.Does the ps3 work with these converters because theres no option for coax only optical.why would a reciever have optical out and not in if its got speakers surely they must know people want to add cd players ,consoles to it