There is provided an input-output protective circuit having more stable IO protective function for use in the liquid crystal display device. The movement database stores 3D spatial positions of surgical tools at times tf and t0; it has moved if its 3D spatial position at time tf differs from that at time t0. A lip extends circumferentially around the frusto-conical body. The controller maintains the bias voltage to the photo-detector at levels which optimize the gain and signal-to-noise ratios for the photo-detector thereby facilitating the decoding of the received signal over a broad range of signal strengths and temperatures. The connector connects to the port of the at least one PCB. The high pass filter is electrically connected in parallel with a series combination of the load coil and the low pass filters to exclude the digital signals from the load coil.