Analog and Digital Signals

Transmission Basics
•In data networking, transmit means to issue signals to the network medium
•Transmission refers to either the process of transmitting or the progress of signals after they have been transmitted
 Analog and Digital Signals
•Information transmitted via analog or digital signals
    –Signal strength proportional to voltage

•In analog signals, voltage varies continuously and appears as a wavy line when graphed over time

    –Wave’s amplitude is a measure of its strength
    –Frequency: number of times wave’s amplitude cycles from starting point, through highest amplitude and lowest amplitude, back to starting point over a fixed period of time
•Measured in Hz  
•Wavelength: distance between corresponding points on a wave’s cycle
•Phase: progress of a wave over time in relationship to a fixed point
•Analog transmission susceptible to transmission flaws such as noise
•Digital signals composed of pulses of precise, positive voltages and zero voltages
   –Positive voltage represents 1 
   –Zero voltage represents 0 
•Binary system: uses 1s and 0s to represent information 
   – Easy to convert between binary and decimal 
•Bit: a single binary signal
•Byte: 8 bits
   –Typically represents one piece of information 
•Overhead: describes non-data information that must accompany data for a signal to be
properly routed and interpreted