Powerline adaptors, adding more?

I currently have a pair of PowerLine adaptors, Tplink 600Mbps. So one is by my router and the other somewhere else. I'd like to add another, but do I need a new pair or just a single one? I don't understand if they are 1:1 or the one nearest the router can act as a kind of switch?

You can just keep adding single ones. And yes, each adapter acts as a switch.

The only wrinkle is if you've enabled encryption, you need to make sure it matches on the new adapter.

You can also generally mix and match brands/speeds, though there are exceptions to this.

Great, thanks for the info. I'll try to find a match to avoid any potential aggravation.

The tpPLC app for Windows is useful too, it shows you the connections speeds between all of the adapters in each direction. And be amazed when moving an adaptor from one socket to another 3feet away changes the speed by 100Mb!

I have not been able to get the Android version of the app to show me anything at all, does not see any of the adaptors.