modem FSK

When flying radio controlled model aeroplanes there is always the chance that a fault will occur in either the transmitter or the receiver, and that the plane will no longer obey the control signals. If one is fortunate, the model will fall near the operator, however it may equally well happen that the plane will remain in flight for a considerable distance, and that the last the unfortunate owner will see of his model is it disappearing over the horizon! The circuit des-cribed here is designed to prevent the latter possibility, and also attempts to lessen the severity of the crash, by ensuring that the model will assume a glide trajectory.