In telephony, beep lines[a] were improvised conference calls hosted over busy signals, loop-around test tones, or certain automated informational service numbers, active in the United States from the early 1950s to the mid-1980s.
[5][6][7][1][3] These lines allowed callers to communicate with up to dozens of other people simultaneously, the conversations often punctuated by the busy tone "beep" and accompanying intercept message.
[10][2][3] The majority of participants were teenagers using these lines to hold informal conversations with strangers in their locality, as well as to collect the phone numbers of potential dates and friends.
[5] As central offices did not send answer supervision to busy signals, conversations hosted over these so-called "beep lines" were toll-free in most cases.
[24][15] Beep lines continued into the 1980s in some rural areas but mostly vanished by the mid-1980s as the vast majority of central offices completed the conversion of their equipment to electronic switching systems.