Abstract: A waveguide-free, simultaneous, bidirectional optical transmission system is disclosed. Each device includes one oscillator for generating a frequency modulated signal. This frequency modulated signal is used for both transmitting a local information signal and for mixing a received modulated signal to produce an intermediate frequency signal of a fixed constant sum frequency. Each device has an FM discriminator for demodulating the intermediate frequency signal to produce a base band signal. Finally, a subtractor is supplied to each device for subtracting the local information signal from the base band signal to recover the received information signal.

Abstract: A device for detecting an object such as a tank in a target area and for causing a horizontal mine to be fired at the object, comprises first and second microphones which detect noise, including noise from a tank, in the target area, in infrared sensor having a directional characteristic which is narrow with respect to the target area and which extends towards the center of the target area to define a target window, and an electronic evaluation unit. The electronic evaluation unit receives acoustic signals from the microphones and calculates a correlation function from the acoustic signal. If a property derived from the calculated correlation function, for example, the correlation or the correlation gradient, exceeds a predetermined threshold, the firing mechanism of the horizontal mine is enabled. If the infrared sensor also detects the presence of an object within its target window, the electronic evaluation unit will cause the horizontal mine to be fired.

Abstract: A helicopter combat device for detecting flying objects and for causing a ground-to-air mine to be fired at them, comprises a microphone which is sensitive to noise generated by a helicopter, an infrared sensor having a directional characteristic which is within the firing cone of the ground-to-air mine, and an electronic evaluation unit which receives and processes electrical signals generated by the microphone and the infrared sensor. The electronic evaluation unit separates the electrical signals received from the microphone into a first band corresponding to noise having a frequency in the range of 5-40 Hz (typical of a rotating rotor of a helicopter), and a second band corresponding to noise having a frequency in the range of 200-1000 Hz (typical of the machine noise of a helicopter).