sampling, quantization, encoding in analog to digital conversion
mean squared error, follows uniform distribution
A = Amax - Amin
prob density function is a rect, A wide, centered on 0, 1/A high
squared error = x-A/2
A/2 = reconstruction level
MSE = int<-A/2,A/2>(E^2)/A = E^3/3A|<-A/2,A.2>
RMSE = sqrt(MSE) = A/2sqrt(3) ~= A/3.4

64Kbps == DS0
multiplexing fun
TDM, time division multiplexing
data link layer (frame is PDU)
framing - encapsulate packet by adding headers/trailer
	- establish frame sync
error detection and control
detection
	CRC
	ARQ - auto repeat request
error checking
	parity fun - even and odd