The HDLC Protocol Controller can be used as a D-channel interface in a digital line card comprised of multiple DNICs.
HDLC协议控制芯片也可以作为D通道接口，用在包含多个DNIC的数字线路卡上；
2
Transfer of OAM (Operations, Administration and Maintenance) information for reserved and permanent services may be provided via a D-channel in another interface structure.
用于预留和永久业务的OAM信息的传递可以通过在其他接口结构中的一个D信道传送。
3
For hardware design, RC filter, voltage sensitive resistor and photoelectric isolation method are used to eliminate interference signal in sampling channel and A/Dchannel.