IMHO no if only using that, because a telefon line needs a DC load
(resistort o transformer of certain DC resistance) to switch to
outgoing line (from 48 drops to 8Vdc) before it can accept DTFM tones
for dialing ..
Maybe he wants to put it alongside some phone that doesn't have
buttons or something, albeit I can't imagine where you'd find
something like that these days. ;-)
Anyway, if that's the case, couldn't he use a pair of, say,
..1 or 1 uF caps from something with a differential output?
(the phone will be providing the DC path - it'd be a little
loud in the earpice, though.
)
Cheers!
Rich