Another SIM900 site with links to resources:
I did not try them all, but the 3 I did try works...
SIM900 AT Command Manual V1.03
SIM900 Hardware Design V2.0
SIM900 Reference Design Guide
Thanks for the links.....I have got these, I bought the module from Microchip but they no longer support it, when the packet came it just had the board in it and details for downloading manual etc as the link, but I could not see how they accessed the buttons and relays and what the jumpers did.
I am old school electronics (62 years old) so I am just learning this type of stuff and AT commands. Perhaps I am missing something in the text?
I did watch the MCE video on youtube and they had a small motor and blade, they accessed the board by calling from a mobile (cellphone) , I zoomed in and it shows that the have a wire from the ring terminal to the relay so that seems pretty straightforward! they took power from the board to the motor via the relay contacts.
All the best