An integrated electro-optical switch based on a planar nematic liquid crystal waveguide has been realized and tested. We present the experimental results obtained with a three-stage device, having as middle stage a thin nematic LC film and two glass waveguides as other stages. The electro-optic al behavior and the response times have been studied for different configurations. The experimental findings show that an additional bias voltage can improve both the transmittivity and the response time of the device (faster than 100 mus). leading to very promising results in the frame of new integrated electro-optical switches. The effect underlying the latter result is not yet understood and probably need some deep insight into liquid crystal physics and into surface interactions. A further analysis is in progress in order to explain an anomalous electro-optical behavior occurred for higher applied voltages.