 When the user pushed a button on the remote control, it struck a bar and clicked, hence they were commonly called a "clicker," but it sounded like a "clink" and the mechanics were similar to a pluck.Each of the four bars emitted a different fundamental frequency with ultrasonic harmonics, and circuits in the television detected these sounds and interpreted them as channel-up, channel-down, sound-on/off, and power-on/off.Later, the rapid decrease in price of transistors made possible cheaper electronic remotes that contained a piezoelectric crystal that was fed by an oscillating electric current at a frequency near or above the upper threshold of human hearing, though still audible to dogs.