Defibrillator Apparatus and Method

An apparatus and method for delivering an electrical defibrillation signal to a heart transcutaneously. The apparatus includes an external transmitter part and implantable receiver part arranged so that an RF pulse can be wirelessly transmitted through a barrier and received internally to apply a defibrillating pulse to a heart. The oscillator and the keying unit are powered via a power source. The external transmitter comprises a capacitor arrangement connected to the power source and a high voltage DC to DC converter, The capacitor is connected through a resonant circuit to circuitry operable to discharge the capacitor through the resonant circuitry and excite the primary coil and cause RF pulse transmission. The primary coil is inductively coupled to the secondary coil of the implantable receiver, to enable instant wireless transmission of the RF pulse across the barrier. The receiver further comprises a resonant circuit, rectification circuitry and filtering circuitry.