| The physical later is concerned with
transmitting raw bits over a communication channel. The design issues have
to do withmaking 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 are
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 downwhen 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. |
