There is no such thing as "...the basic telephone circuit..", insofar as there is no engineering standard of that title, nor pervasive enough real-world implementation to warrant use of the singular, royal, "the".
(What's that that's been said about the "tyranny of the or, vs. the magic of the and"?)
Folderol aside, if what you're talking about is the classic analog tip & ring, or common RJ-11 pinouts, etc. search blackbox.com, or look in one of their catalogs.
If, on the other extreme, you ARE looking for specs, and are asking about say, the designed-in attenuation-driven distance limitations for a four-wire 4 kHz ground-start copper voice trunk, or a four-wire copper T-1, then I recommend a general web search, a visit to whatis.com to surf their links, or ..........
...the addition of detail to your original request in order to make it easier for your fellow users of this site to better understand what you're in specific need of.