hi! I'm joseph
I know where to buy that.But first i will ask you from what country you live?
Because here in Philippines i have a electronic supply (store) and it only cost
22$ each
hi,i'm joseph
I don't know who creted it but I know a site that gives it schematic-diagram
If you're interested this is the exact site where you can see it:
http://www.redcircuits.com/Health.htm
IF you find difficulties to download it just save it's schematic-diagram in your
computer
hi,I'm joseph
I downloaded a software where you can easily search for datasheets.If you
like to dowload it also here is the site where you can download it free "http://www.nteinc.com/qc12/"