An electrical isolation barrier for use in a Data Access Arrangement uses a high frequency (HF) transformer 24 to provide isolation. An input signal, which may be analog or digital, is connected to a modulator. The analog output of the modulator is connected to the input of the HF transformer. The output of the HF transformer is connected to the input of a demodulator. Simple amplitude modulation can be used in the modulator to modulate the input signal to the frequency range of operation of the HF transformer. A simple low pass filter may be incorporated in the demodulator to remove harmonic distortion caused by the HF transformer. The output signal of the demodulator is substantially the same as input signal.