The most popular such device is the computer - the very device with which you asked that question, and with which I am answering it.
telegraph
it is passing or transmitting a message or information, to exchange ideas
a communication device
The three processes used by sender-receivers are encoding (converting information into a message), transmitting (sending the message through a chosen channel), and decoding (interpreting the message by the receiver).
a communication device
DSL
telephone
It's called a global multicast, and you're transmitting to all reachable nodes.
routers
routers
The light on your device may be blinking to indicate that it is receiving or transmitting data, or to alert you to a notification or a low battery.