equipment engaged tone

An audible signal sent to a caller to indicate that a call cannot be completed, owing to congestion in some part of the network. In many systems busy tone is used for this purpose.; 由于網絡某些部分發生了阻塞故障,送給呼叫者的一種音頻信號,表示呼叫失敗。在許多 系統中都使用忙音。