Coupled Approach??

[VEJ]

I'am looking for the definition of an coupled approach.

Reason:
The airplane that I am flying now (DHC-8 315) has a limitation on the autopilot for single-engine coupled approaches and for an coupled back-course approach.

Now do I want to know if an coupled approach only applies to precision approaches or also to non-precision approaches.

(If possible a link to an "official" website)

Thanks for the help,

VEJ