Two Way Communication
Communication may be one-way, when no reply is wanted or expected. For example, a public notice stating ‘TURN OFF LIGHTS’ is a command or an order which does not demand a response. However, if people do not like the message, they may respond by writing rude words on it!
Most communications are two-way, with some feedback, or response, required from the receiver.
If some official response was wanted to the message about turning off lights, a different means of communication would have to be used. Instead of putting up a notice, a memorandum, or a brief written message on a form, would have to be sent to the heads of all departments asking them to ensure that all lights should be turned off when not in use.
The sender could ask for the message to be acknowledged, or for the heads of departments to report what action they were taking to put the order into effect.
If the sender wanted to make the message more persuasive, a reason for the request could be given, which might be the need to reduce costs.