After rigorous research, and serious testing, phone company, Bell Systems, introduced the first touch tone phone in 1963.

经过严格的研究和认真的测试，电话公司 Bell Systems 在 1963 年推出了第一部按键式电话。

They were tones that sound like the touch tone you make on your phone, but with different frequencies so you can make them.

这样发出的声音信号听起来就像你在电话上发出的按键音，但频率不同，能够模拟制作出来。