LBT Line Busy Tone

busy line

Double line-line voltage control

LB Line Busy

line-line extreme distance

line-line topological relation in traffic network

on-line line loss

tone-line effects method

tone-line technique

BT Busy Tone

busy tone

Busy Tone BT

busy tone detecting

busy tone trunk

channel busy tone

dual busy tone multiple access

group busy tone

loss-free line (=lossless line =lossless transmission line)

SDSL Single-Line Digital Subscriber Line，Single-Line DSL