A:Answer I am an end-user so cannot answer all questions about what is available from the market. What I do know is that I believe they are sold in pairs because one is needed as a transmitter, and one us used at the receiver. That being said, I also know that they will work successfully in odd numbers. I presently have 3 in use, one, of course as the transmitter, one as a receiver for my TV, and one as a receiver for a laptop that consistently has issues staying connected to the WIFI. Extending the virtual Ethernet to that laptop indirectly solved its connection issues.
I might suggest that if you have need for one, you might have need for more in the near future, as I did. I was not able to find a single unit for sale, though I must admit I did not do an exhaustive search. I did suspect that I would have a need for expansion in the future so didn't shy away from having a spare laying around. (At some point in the near future, I plan to update the TV in the guest bedroom from dumb to smart, and when that happens, I will put the spare unit to use.)
I would also suggest that when you select a supplier, be sure to confirm that any units you buy meet the IEEE standard for Ethernet-over-power lines. That way you can be sure that all units you buy will work together, even if sourced from different manufacturers.
