The mathematical representation of any physical phenomenon are most of the time differential equations. This time-domain representation is not always easy to deal with specially if the degree of the equations is high. Laplace and Z-transforms, LPC and TLM are widely used to deal with the modeling of these physical phenomena . This book deals with mainly Laplace and Z-transforms introduction, then some examples in hydraulic, mechanics, electronics, acoustics and electric analogy of the universal gravitation fields.