direct-current ringer是什么意思

网络释义

1)direct-current ringer,直流振铃器2)DC signalling,直流振铃3)acldc ringing,交直流振铃4)direct current ringing,直流振铃<声>5)ac/dc ringing,交流/直流振铃6)DC ringing,直流振铃[电话]