| PHYSICAL |
| Vedrana Boljkovac Ped-Inf 3 god. |
Tamara Crncic Inf-Fil 3.god |
Elena Grskovic Inf-Eng 3.god |
 |
|
The physical later is concerned with transmitting raw bits over a
communication channel. The design issues have to do with making sure that
when one side sends a 1 bit, it is received by the other side as a 1 bit,
not as a 0 bit. Typical questions here ar e how many volts should be used to
represent a 1 and how many for a 0, how many microseconds a bit lasts,
whether transmission may proceed simultaneously in both directions, how the
initial connection is established and how it is torn down when both sides
are finished, and how many pins the network connector has and what each pin
is used for. The design issues here deal largely with mechanical,
electrical, and procedural interfaces, and the physical transmission medium,
which lies below the physical layer. Physical layer design can properly be
considered to be within the domain of the electrical engineer.
Example : The X.21 digital interface. |