ABSTRACT
Equalizers are precise tone controls, changing the timbre of a sound by making one part of the spectrum louder or another softer. But they didn’t start out that way.
It began, as do so many other things in this book, with the phone company. In the 1920s, broadcasters would lease cables from the phone company, first for remote broadcasts within the same city, and later for intercity hookups and networks. But the wires that were okay for phone calls had too much high-frequency loss for radio. So a telco engineer would send test tones at various frequencies from a remote location. A colleague would sit at the other end of the line with a voltmeter, and he would clip capacitors and inductors to the line until the voltage was equal for each tone. When the tones were equalled, they declared the line equalized.
