The element y 22 {\displaystyle y_{22}\,} is the short circuit mechanical admittance, that is, the admittance presented by the mechanical side of the transducer when zero voltage (short circuit) is applied to the electrical side. The element y 11 {\displaystyle y_{11}\,} , conversely, is the unloaded electrical admittance, that is, the admittance presented to the electrical side when the mechanical side is not driving a load (zero force). The remaining two elements, y 21 {\displaystyle y_{21}\,} and y 12 {\displaystyle y_{12}\,} , describe the transducer forward and reverse transfer functions respectively.