• Signals are time-varying voltages or currents.
• Sinusoidal signals - Time functions, amplitude, frequency and phase.
• v(t) = A sin(wt + f)
• The implications of having different frequencies.  The possibility of frequency dependent circuits.
• Sinusoidal signals add differently when they do not have the same phase.  There is a need to take care if you have to add two sinusoids with different phases.

2. Signal Parameters

• Sinusoidal signals have three parameters.
• Amplitude (A) - how large they are, i.e. the A in the expression above.
• Frequency (f) - the number of cycles that the sine signal goes through each second.
• The angular frequency is w given by: w = 2pf
• Phase ( f) - An angular measure of the difference in the time of peaks and zero crossings between a sinusoidal signal and an arbitrary reference sinusoid of the same frequency.