# Conditions for Reciprocity and Symmetry

A network is said to be reciprocal if the ratio of the response transform to the excitation transform is invariant to an interchange of the positions of the excitation and response of the network.

A two-port network will be reciprocal if the interchange of an ideal voltage source at one port with an ideal current source at the other port does not alter the ammeter reading.

A two-port network is said to be symmetrical if the input and output ports can be interchanged without altering the port voltages and currents.

Table:Conditions of Reciprocity and Symmetry in terms of different Two-Port Parameters

 Parameter Condition of Reciprocity Condition of Symmetry z z12= z21 z11 = z22 y y12 = y21 y11 = y22 T (ABCD) (AD â€“ BC) = 1 A = D h h12 = â€“h21 (h11h22 â€“ h12h21) = 1