Telephone No Number Or Signal

A telephone signal you can hear when a phone line is busy, when there is no such number available or the number is unobtainable. This means the phone call cannot reach the other end at this particular moment. Although this sound is already outdated for most mobile phone providers as it is not used for mobile phones any more, it can appear for landlines and also fits movies and videos that take place in the 60s, 70s, 80s or 90s. The three notes can be looped easily.