@David-TP Thanks for the informative response. Not the answer I wanted but the facts are always better. Now I know what I'm dealing with. One additional question: What indoor access point will extend...

My home network is set up in the following way; ADSL to a Router Router to DECO x20 DECO x20 to a TP-Link switch DECO x20 to 2 DECO x20 wifi mesh in main house DECO x20 to 1 DECO x20 in Guesthouse...