Answer: busysignal

AnswerCrossword Clue
BUSYSIGNALConversation barrier
BUSYSIGNALPhone's "try later"
BUSYSIGNALSound of a communication failure
BUSYSIGNALTelephone sound effect.
BUSYSIGNALCaller's annoyance
BUSYSIGNALA holdup
BUSYSIGNALPart of phone tag, sometimes
BUSYSIGNALSemaphore on the go?