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.