Interactive voice response (IVR) is a technology that allows telephone users to interact with a computer-operated telephone system through the use of voice and DTMF tones input with a keypad. In telecommunications, IVR allows customers to interact with a company's host system via a telephone keypad or by speech recognition, after which services can be inquired about through the IVR dialogue. IVR systems can respond with pre-recorded or dynamically generated audio to further direct users on how to proceed. IVR systems deployed in the network are sized to handle large call volumes and also used for outbound calling as IVR systems are more intelligent than many predictive dialer systems. IVR systems can be used standing alone to create self-service solutions for mobile purchases, banking payments, services, retail orders, utilities, travel information and weather conditions. In combination with systems such an automated attendant and ACD, call routing can be optimized for a better caller experience and workforce efficiency. IVR systems are often combined with automated attendant functionality. The term voice response unit (VRU) is sometimes used as well. Despite the increase in IVR technology during the 1970s, the technology was considered complex and expensive for automating tasks in call centers. Early voice response systems were DSP technology based and limited to small vocabularies. In the early 1980s, Leon Ferber's Perception Technology became the first mainstream market competitor, after hard drive technology (read/write random-access to digitized voice data) had reached a cost-effective price point. At that time, a system could store digitized speech on disk, play the appropriate spoken message, and process the human's DTMF response. As call centers began to migrate to multimedia in the late 1990s, companies started to invest in computer telephony integration (CTI) with IVR systems. IVR became vital for call centers deploying universal queuing and routing solutions and acted as an agent which collected customer data to enable intelligent routing decisions.