When Mediated Communication Occurs?

Is mediated communication occurs through the wall chalking or not? if not then in what part of communication level wall chalking exist?

Mediated Communication is level of communication which occurs when two or few people use some transitional means to deliver their message. Such as telephone, radio, radar, computer, close circuit TV, Communication satellite etc. However, letters, reports, forms, wall chalking and interoffice memos are also used as a tool for mediated communication.