Daniel N. Flickinger introduced the first parametric equalizer in early 1971. His design leveraged the high performance op-amp of his own design, the 535 series (USPTO #3727896) to achieve filtering circuits that were before impossible. Flickinger's patent (USPTO #3752928) from early in 1971 showed the circuit topology that would come to dominate audio equalization until the present day, as well as the theoretical underpinnings of the elegant circuit. Instead of slide potentiometers working on individual bands of frequency, or rotary switches, Flickinger's circuit allowed completely arbitrary selection of frequency and cut/boost level in three overlapping bands over the entire audio spectrum. Six knobs on his early EQ's would control these sweepable filters. Up to six switches were incorporated to select shelving on the high and low bands, and bypassing for any unused band for the purest signal path. His original model boasts specifications that are seldom met today. [ citation needed ]
Many Latin American and Caribbean (LAC) nations have experienced monumental growth and change in the past several decades, and USAID has partnered with these countries to make important progress. Despite the global financial crisis, the region averaged a three percent annual increase in economic growth between 2000 and 2012. Health indicators have greatly improved in the region: for example, maternal mortality has fallen from 140 to 81 deaths per 100,000 live births since 1990. Political advances have been notable, as well: free elections, vibrant civil society, and responsive governments are mostly the norm.