双向振铃中继电路

two-way trunk circuit two-way mirror way circuit trunk record circuit trunk junction circuit incoming trunk circuit toll line trunk circuit trunk demand circuit outgoing trunk circuit ring circuit two-way ring down trunk circuit private line two-way trunk circuit two-way trunk line ring-down trunk ring-down trunk signaling two-way duplex circuit two way circuit two-way circuit two-way telephone circuit two-way half-duplex circuit two-way double-triode clamp circuit way down