A locking switch (102, 202), comprising: a solenoid-driven locking bolt configured to engage with an engagement hole (112, 410) of a locking tongue (108, 412) when advanced to a locking position; and an inductive sensor system configured to detect that the locking bolt has advanced to the locking position, wherein the inductive sensor system comprises a tank circuit comprising an inductive coil and a capacitor, the inductive coil oriented to receive the locking bolt when the locking bolt is advanced to the locking position, a converter configured to convert a frequency of a current signal on the tank circuit to a digital frequency value, and a master controller configured to generate a lock detection signal in response to determining that a shift in the digital frequency value corresponds to an expected frequency shift of the current signal induced by the inductive coil in response to advancement of the locking bolt; and a diagnostic system configured to confirm operation of the inductive sensor system, the diagnostic system comprising a diagnostic capacitor and a diagnostic switch configured to connect the diagnostic capacitor to the tank circuit in parallel with the capacitor, wherein the diagnostic capacitor has a capacitance that, in response to connection of the diagnostic capacitor to the tank circuit in parallel with the capacitor, causes the frequency of the current signal to shift by the expected frequency shift induced by the inductive coil in response to advancement of the locking bolt. a solenoid-driven locking bolt configured to engage with an engagement hole (112, 410) of a locking tongue (108, 412) when advanced to a locking position; and an inductive sensor system configured to detect that the locking bolt has advanced to the locking position, wherein the inductive sensor system comprises a tank circuit comprising an inductive coil and a capacitor, the inductive coil oriented to receive the locking bolt when the locking bolt is advanced to the locking position, a converter configured to convert a frequency of a current signal on the tank circuit to a digital frequency value, and a master controller configured to generate a lock detection signal in response to determining that a shift in the digital frequency value corresponds to an expected frequency shift of the current signal induced by the inductive coil in response to advancement of the locking bolt; and a tank circuit comprising an inductive coil and a capacitor, the inductive coil oriented to receive the locking bolt when the locking bolt is advanced to the locking position, a converter configured to convert a frequency of a current signal on the tank circuit to a digital frequency value, and a master controller configured to generate a lock detection signal in response to determining that a shift in the digital frequency value corresponds to an expected frequency shift of the current signal induced by the inductive coil in response to advancement of the locking bolt; and a diagnostic system configured to confirm operation of the inductive sensor system, the diagnostic system comprising a diagnostic capacitor and a diagnostic switch configured to connect the diagnostic capacitor to the tank circuit in parallel with the capacitor, wherein the diagnostic capacitor has a capacitance that, in response to connection of the diagnostic capacitor to the tank circuit in parallel with the capacitor, causes the frequency of the current signal to shift by the expected frequency shift induced by the inductive coil in response to advancement of the locking bolt.