A special type of device which uses an ordinary telephone with a computer is

An acoustic coupler is a device which sends and receives computer data through a telephone line using sounds rather than electrical signals. The devices were popular in the early days of internet use when traditional modems were not always practical. Today, they are mainly seen in countries with less advanced telecommunications networks, and in equipment used by deaf people to make telephone calls.

An acoustic couple is an interface device for coupling electrical signals by acoustical means—usually into and out of a telephone.