dialling tone

英 [ˈdaɪəlɪŋ təʊn]

美 [ˈdaɪəlɪŋ toʊn]

n.  (电话的)拨号音

牛津词典

noun

• （电话的）拨号音
  the sound that you hear when you pick up a telephone that means you can make a call

柯林斯词典

• (电话的)拨号音
  Thedialling toneis the noise which you hear when you pick up a telephone receiver and which means that you can dial the number you want.

in AM, use 美国英语用 dial tone