 In all of the circuits given below it is assumed that the generator and load impedances are purely resistive (though not necessarily equal) and that the attenuator circuit is required to perfectly match to these.The symbols used for these impedances are;

Popular values of impedance are 600Ω in telecommucations and audio, 75Ω for video and dipole antennae, 50Ω for RF

The voltage transfer function, "A", is,

While the inverse of this is the loss, "L", of the attenuator,

The value of attenuation is normally marked on the attenuator as its loss, "L"dB, in decibels (dB).The relationship with "L" is;

Popular values of attenuator are 3dB, 6dB, 10dB, 20dB and 40dB.