The year 1973 sees the introduction of phone fax service. The phone fax is a device that allows subscribers to exchange facsimile transmissions over telephone lines, and offers advantages over existing means of transmitting information including telephone, mail and telex. Revision in the system of use of public telephone lines present the opportunity for fax service to gain widespread acceptance. Using flat-bed scanning techniques, the standard transmission time for one A4 page is around 6 minutes.