Does anyone know how the electronic tacho works in the Beech Duchess? I am looking to understand how the pick up works that senses the engine revolutions from the toothed ring gear. I need to find out what the sensor part number is and if there is a current equivalent part available to purchase. My guess is that the device is a magnetic speed sensor with a two wire output that provides an ac voltage from the coil wrapped around a magnetic core when the toothed ring gear rotates. My questions are, what is the voltage range output? and what is the impedance of the coil? If any one knows.