The terms Y are known as Admitting Parameters, and its unit of measure is the SIEMENS.

The parameters values can be calculated by making V₁ = 0, that is, short-circuited input port or V₂ = 0, which means short-circuited output port. Therefore, these parameters are known as Short Circuit Admittance Parameters.

We can define the parameters as:

a) Y₁₁ ⇒ Short-circuit input admittance.

b) Y₁₂ ⇒ Short-circuit transfer admittance from Port 2 to Port 1.

c) Y₂₁ ⇒ Short-circuit transfer admittance from Port 1 to Port 2.

d) Y₂₂ ⇒ Admittance of short-circuit output.

Therefore, if we want to calculate Y₁₁ and Y₂₁ we should connect a current source I₁to port 1 and short-circuit port 2. Thus, determining the values of V₁ e I₂, together with the value of I₁ which we already know, we calculate the parameters.

And to calculate Y₂₂ and Y₁₂, we use the same reasoning, connecting a current source I₂ to port 2 and short-circuiting port 1. As we know the value of I₂ and calculating V₁ and I₂, we can determine the parameters.

Similar to the Parameters Z , if Y₁₂ = Y₂₁ we say that the circuit is PASSIVE or RECIPROCAL.

Thus, when a circuit is of this type, we can represent it by the circuit in the Figure 32-02.

If the circuit is not Reciprocal or Passive, that is, have dependent sources, then we have to modify the model. See the Figure 32-03 an equivalent circuit model for general cases.

Note that this circuit is derived directly from the equations of the Parameters Y , given at the beginning of the page.

There is a relation between the parameters Y and Z given by the equations: