由电端机经电缆输送给光端机输入电路的PCM电信号的码型，称为输入接口码型，单极性不归零码，CMI码，HDB3码等-By electric end machine through a cable to optical transceiver type of PCM signal input circuit, known as the input interface type, single polarity is not zero yards, CMI code, HDB3 code, etc