Kind of answered it mostly, here. http://www.differencebetween.net/technology/difference-between-rj11-and-rj12/
I get my RJ-11's from allelectronics.com , CAT#cmp-6, 10 for $3, 6 wire flat telephone cable 50' for $6 and I also bought the crimping tool there cat #MPCPT-6.
RJ11, RJ12, RJ25.... You will find any (or all) of them out there, and (particularly for RJ12) definitions vary all over the map. Whatever the nomenclature used, you want a 6 position modular connector with all 6 contacts populated (i.e., 6p6c). In many cases, an RJ11 will be 6p4c (or even 6p2c). Best to evaluate by inspection.
