Q&A
Many articles in this series are intended to Q & A way to solve the difficult point.
Question
There are two issues:
- Transmission medium is the physical layer do?
- If not, what is the main difference between the transmission medium and the physical layer is?
Answer
First of all must be clear that the transmission medium (transmission medium) than the physical layer.
Look transmission medium, which is the physical channel between a transmitting device and a receiving device (oriented and can be divided into two types of non-oriented).
Typically a transmission media: twisted pair, coaxial cable, fiber, wireless transmission media (radio waves, microwaves, infrared, laser, etc.).
Look at what is the physical layer, the physical layer whether it is in the five-story architecture OSI seven-layer architecture is still in widespread use, are the bottom.
The physical layer transmission media is not talking, but the device, such as a repeater (repeater), a hub (the Hub) and the like, are used to transfer media.
The physical layer signal is transmitted, the emphasis is on the 0/1 bit abstract, the signals transmitted in the transmission medium. Unfortunately, only a medium transmission medium, a physical only "see" a signal of the form itself, but does not recognize these signals (not know what is 0 is 1). And the physical layer interface specified mechanical properties, electrical properties, functional properties, protocol properties, so that the transmission medium can pass over into a bit identifying signal 0/1, and therefore can communicate.
Tips
After reading the content, you clear?
In fact, it seems the physical layer in a lot of beginners, probably those of electromagnetism itself physically, but in fact it really was not.
You have to think, ah, after all, is part of the physical layer network architecture of the meter, the architecture itself is abstracted. Therefore, even if physical layer is the lowest layer, the physical depth not itself, it also shields the complexity of a transmission electric signal itself to identify what the physical medium for transferring via a predetermined interface specifications, and discretized into 0/1 bit, it is the signal, it makes sense to communicate.
