The L network consists of a series impedance, Z, and a shunt admittance, Y.

At resonance, the series impedance of the two elements is at a minimum and the parallel impedance is at maximum.

The Heaviside condition is that the series impedance, Z, must be proportional to the shunt admittance, Y, at all frequencies.

Thévenin equivalent - Any linear two-terminal circuit can be replaced by a single voltage source and a series impedance.

This introduces error but allows combination of primary and referred secondary resistances and reactances by simple summation as two series impedances.

Thévenin's theorem states that any two-terminal network can be reduced to an ideal voltage generator plus a series impedance.

The balance is achieved in the same way as a balanced full bridged T section by placing half of the series impedance in, what was, the common conductor.

Conversely, on the outer edge of the choke ditch, at the point where the two flanges come into physical contact, the ditch presents a high series impedance.

If the resistive part of the series impedance of the antenna is , the power fed to the antenna is .

Another method of determining the series impedance of a real transformer is the short circuit test.