Which device transmits signals from one station to another directly along a wire without the use of radio waves?

The landline phone is the correct answer because it relies on physical wires to transmit voice signals directly from one station to another. This communication method uses copper or fiber-optic cables to send the electrical or optical signals, ensuring a reliable and straightforward connection that does not depend on radio waves or other wireless technologies.

In contrast, mobile radios and satellite phones communicate over radio waves, which can traverse the air and do not require a physical connection between the devices. VoIP (Voice over Internet Protocol) service, while it can provide voice communication, primarily operates over internet connections and may rely on various transmission methods, including both wired and wireless signals. Thus, the landline phone remains unique in its direct wired communication approach, distinguishing it from the other options that utilize different transmission techniques.