I haven't figured out how to call my other Alexa Echo or Dot units... (say I wanted to call my wife on the Echo dot in the kitchen from my echo dot here at my office.)
To use the "intercom" function just say Alexa "call home", the ring will turn green on all of your units, then you just say alexa answer and your connected. You can't select which units, it connects all of them.
And if you add the Dish Skill through the Alexa App, you can control your Hopper through Alexa.
Alexa tune to channel 3...