Thanx pix,
I am clear now with duplex communication. I also need to know the technique by which two exchanges interact with each other. For example, we speak that the 64kbps speech is carried by a device in E1. How it is carried. In electricity, the current will flow from higher potential to lower potential. Is there any similar technology in speech transfer also. I dont want to restrict it to speech. I want to be cleared with signaling link also.
regards,
ram