Correction
"To begin, nothing on the units indicate which is which, but it's pretty obvious which is the Sender and which the Receiver once you look at the connections on back. The Sender has a HDMI output and a plug for power, while the Receiver has a HDMI input, plug for power as well as left/right analog audio outputs (note: this output is only active when the audio being carried along by the HDMI source is 2 channel LPCM)."
I think you have that backwards; the Sender has the HDMI input, and the Receiver has the HDMI output. Which kind of calls into question how "obvious" it is.