What is the function of a transmission machine that scans a document for sending over a phone line?

The function of a transmission machine that scans a document for sending over a phone line is primarily associated with a fax machine. A fax machine converts physical documents into digital images, which it then transmits over a phone line to another fax machine. This process involves scanning the document to capture its content and then encoding it for transmission, making it accessible to the recipient in printed form.

While a photocopier can create duplicates of documents and a scanner can digitize documents for storage or editing, they do not have the capability to send those documents over a phone line. Similarly, a printer is utilized to produce physical copies of digital files but does not have the functionality to transmit documents. The unique capability of a fax machine to both scan and send documents over telephone lines clearly defines its function in this context.