dial tone
Telephony signal sent by a telephone exchange or private branch exchange (PBX) to a terminating device, such as a telephone
en-GB/ˈdaɪəl ˈtəʊn/
en-US/ˈdaɪl ˈtoʊn/
Telephony signal sent by a telephone exchange or private branch exchange (PBX) to a terminating device, such as a telephone