So you can pick up the phone, you hear a dial tone, but its just a fake-out. It's a WAV file of a dial tone, just to reassure you that the world hasn't ended.
拿起电话以后，你能听到有拨号音 但是那个拨号音是假的，那就是一个拨号音的音频文件 好让你知道世界末日还没有来临