ATA is an abbreviation for Analog Telephone Adapter. An analog telephone adapter is a device for connecting traditional analog telephones, fax machines, and similar customer-premise devices to a digital telephone system or a voice over IP telephony network. An ATA is often built into a small enclosure with an internal or external power adapter, an Ethernet port, one or more foreign exchange station (FXS) telephone ports. Such devices may also have a foreign exchange office (FXO) interface for providing alternative access to traditional land line telephone service. The ATA provides dial tone and other standard telephone supervisory signaling to the telephone connected to a modular jack. Source: Wikipedia