Transmission is about communication, and people have communicated for a long time. For example, smoke signals or the presence or absence of fire communicated information in millennia past. Information was also transmitted in antiquity via light-emitting devices. In both of these examples, however, communication depended on the ability of the parties involved to see each other; a cloud in the way would impede effective transmission.

Thus, people had to free themselves from this line-of-sight constraint, and sending a signal over a wire offered a solution. What was sent was no longer a visible signal, but rather voltage on a wire. Wire enabled the signal to travel vast distances without losing strength. How does a message originate and terminate such a line? The telephone provided a convenient user interface to the network.