A family of extremely popular devices from Amazon.com that combines a wireless speaker, music streamer and the Alexa virtual assistant in one unit. In the millions of homes that have multiple Echos, individual units can be configured to play their own tunes. Echo devices are also used to control lights and home appliances (see smart home).Although an Echo is the hardware, and Alexa is the service, people mostly refer to the device as Alexa. Introduced in 2015, several variations followed (see all models below).Voice Calling and MessagingIn 2017, voice calling and messaging (both text and voice) were added so that users can call and message other Echo devices. In addition, Alexa users can install the Alexa app in their smartphone, which integrates the contact list and allows hands-free calling from Echo devices to the phone.Intercom CapabilityA year later, Echos were enabled to broadcast messages to all other Echos ("dinner is ready"). In the same year, Amazon put Echo on the road (see Echo Auto)."Alexa - What's the Capital of Maine?"Always connected via Wi-Fi, when any of the Echo's seven microphones hears the word "Alexa" from across the room, it "wakes up," emits an audible signal and waits for a question. Most people use the default Alexa wake word; however, "Amazon," "Echo" or "computer" can be selected instead.The Echo AppAvailable for the user's desktop and mobile devices, the app provides device setup and logs all questions and answers. The app also manages a to-do list, timer, alarms and music sources, and it accepts general questions as well. See Alexa Voice Service, virtual assistant, Bluetooth speaker and Amazon Dash.