A teleprinter is a device used for transmitting typed messages quickly over a long distance. It is similar to a typewriter but is connected to a communication network that allows the messages to be transmitted over a distance. The teleprinter works by converting the typed characters into electrical signals that are transmitted over a wire or radio signal to another teleprinter at the receiving end.
Teleprinters were widely used in the past for sending messages between different locations, such as between news agencies or government offices. They were also used for communicating with remote locations, such as ships at sea. Teleprinters were an important tool for transmitting messages quickly before the advent of modern communication technologies such as email and instant messaging.
Therefore, the correct answer to the question is that a teleprinter is used to transmit typed messages quickly over a long distance. It is not used for transmitting important documents through the post office, data to and from a computer, messages to areas within a locality, or information within a bank.