  In this report, we generalize Shannon's push-to-talk two-way channel
(PTT-TWC) by allowing reliable full-duplex transmission as well as noisy
reception in the half-duplex (PTT) mode. Viewing a PTT-TWC as two
state-dependent one-way channels, we introduce a channel symmetry property
pertaining to the one-way channels. Shannon's TWC capacity inner bound is shown
to be tight for the generalized model under this symmetry property. We also
analytically derive the capacity region, which is shown to be the convex hull
of (at most) 4 rate pairs. Examples that illustrate different shapes of the
capacity region are given, and efficient transmission schemes are discussed via
the examples.
