There are several hundred telemarketing call centers in the U.S., with the majority of telemarketing calls being dialed by a computer known as an auto dialer or predictive dialer. Predictive dialers can dial 3-5 numbers simultaneously and can make as many as 500,000 calls between 8 a.m. and 9 p.m. When you answer your phone, the computer connects you to a live telemarketer who tries to sell you something. If you are not home or if the computer gets your answering machine, your number will be put back in the database to be called again later.