over the sound of the busy signal
... that American teenagers of the 1960s and 1970s used to chat and arrange dates over the sound of the busy signal?
... that American teenagers of the 1960s and 1970s used to chat and arrange dates <b id="mwBqA"><a href="./Beep_line" id="mwBqE" rel="mw:WikiLink" title="Beep line">over the sound of the busy signal</a></b>?