AT&T expanded its online push on Monday, announcing it acquired advertising technology firm Ingenio.

Ingenio allows phone marketers to measure the effectiveness of ad campaigns by keeping track of phone calls made to advertisers based on phone numbers used in ads. The technology used by Ingenio is known as pay-per-call.

AT&T will incorporate Ingenio's technology into its search and directory products like, AT&T Real Yellow Pages and 1-800-yellow-pages.

The acquisition of Ingenio will allow AT&T to expand its directory and local search business.

Ingenio was providing technology that allowed online marketers to charge for every call to a 1-800 phone number listed on an advertisement.

Ingenio currently has deals with AOL and Microsoft Mobile to provide pay-per-call advertisements.