 The image admittance of the input is,

and the image impedance of the output is,

The loss of the L section when terminated in its image impedances is,

where the image parameter transmission function, "γ"L is given by,

The loss of this L section in the reverse direction is given by,

For an attenuator, "Z" and "Y" are simple resistors and "γ" becomes the image parameter attenuation (that is, the attenuation when terminated with the image impedances) in nepers.A Π pad can be viewed as being two L sections back-to-back as shown in figure 3.Most commonly, the generator and load impedances are equal so that and a symmetrical Π pad is used.