Hi,
Having surfed for a datasheet for a Mitsubishi PA unit named M57741,
all I found was "pay-only" info.
If someone know where to find it, I would like to hear :-)
OM LA8AK seems to know a thing or two about how to use the M57741,
so you could try this page of his site.
http://home.online.no/~la8ak/d25.htm
73 de Joe, G3LLV