The switching device includes a sensing unit configured to detect the level of leakage of the capacitor so that the switching device disconnects the capacitor electrically if the leakage current exceeds a predetermined level.

The carrier leakage level in an output signal of the modulator is measured and in response base band dc offset voltages are adjusted to minimize the carrier leakage.

The fittings (20, 21) are designed for quick connect/disconnect, and for minimal or no leakage.

The ferroelectric (5) establishes the level of leakage of the pn junction to provide a gate-controlled diode or transistor device.