International Telephone and Telegraph Corporation

Itt Corporation

Itt Electro Optical Products, a Division of Itt Corporation

Joseph Reed

Joseph N Caserta

James Hoge Bowen

William D Mims

An image intensifier tube having an electromagnetic interference protection arrangement. The protection is accomplished by shielding the tube and filtering the power supply. Shielding is performed by means of a conductive metallic coating which surrounds the image intensifier tube housing. Filtering is accomplished by using capacitors to short the interference to ground.

Electromagnetic interference protection for image intensifier tube

There is disclosed a high light level cutoff apparatus for use with night vision devices. The apparatus employs a digital method of timing implemented by a divider counter responsive to a crystal controlled input frequency which essentially controls a latch to produce an automatic shutoff of a night vision device during high light ambient conditions which conditions would undesirably reduce the effective life of such a night vision device. The circuitry disclosed utilizes a digital method of clocking and employs the latching relay as indicated which is operated by the digital counter. The circuitry provides a feed back from the latching relay which resets the night vision system so that it will re-operate if a transient accidentally serves to operate the goggles while the light level is in a high state. The circuitry provides a precise timing level via the counter which can be selected to provide extended time out periods from milliseconds to at least several minutes, circumventing many of the disadvantages of prior art devices.

High light level cutoff apparatus for use with night vision devices

A demodulator of the type employed in a 'zero-IF' system uses a local oscillator for providing quadrature output signals at the center frequency of a received signal to be demodulated. The demodulator has first and second mixers for separately mixing the received signal with the quadrature signals to provide a first and second output signal each in quadrature at the outputs of said mixers. These signals are low pass filtered. The demodulator includes third and fourth mixers with each mixer respectively receiving at an input one of the first and second low pass signals. At another input the mixers receive third and fourth signals. The third and fourth signals are derived from mixing a variable controlled oscillator (VCO) signal with local oscillator quadrature signals the frequency of said is independent of the center frequency of the received signal. The outputs of the third and fourth mixers are applied to the inputs of a difference amplifier, the output of which controls the frequency of the VCO in an automatic frequency control mode (AFC) to cause the output of the difference amplifier to provide demodulation of an FM signal. Additional mixers are provided which mix the first and second low pass signals respectively with the fourth and third signals, with the signals appearing at the outputs of such additional mixers being summed to provide demonstration of an AM signal independently of the FM demodulation.

Baseband demodulator for FM and/or AM signals

Apparatus is depicted which enables the sampling of the phase angle of a modulated signal and manipulates the sample signals to demodulate the same. The apparatus is particularly adaptable for use in demodulating the I and Q channel signals of a zero IF receiver. The system contains an angle sensing circuit which combines the I and Q channel signals in differential form to produce a series of output signals of an angular range indicative of the present value of the instanteous phase. The signals from the angle detector are coupled to an octant decoder which operates to determine the particular octant that the angle is to be included in. In the present system eight octants are used, each comprising 45.degree.. The octant decoder determines which octant the angle belongs in and assigns a predetermined angle value to that angle. In one embodiment, the assigned angle values are 0.degree., 45.degree., 90.degree., 135.degree., 180.degree., 225.degree., 270.degree. or 315.degree.. The value of the assigned angles are then sampled by means of a clock at a high frequency rate whereby the resultant pulses indicative of the angles are then processed as differentiated to produce an output signal indicative of the information content on the original signal.

Zero IF receiver AM/FM/PM demodulator using sampling techniques

A demodulator of the type employed in a 'zero-IF' system uses a local oscillator for providing guadrature output signals at the center frequency of an FM signal to be demodulated. The demodulator has first and second mixers for separately mixing the FM signal with the quadrature signals to provide a first and second output signal each in quadrature at the outputs of said mixers. These signals are low pass filtered. The demodulator includes third and fourth mixers with each mixer receiving at an input one of the low pass signals. At another input the mixers receive third and fourth signals. The third and fourth signals are derived from mixing a variable controlled oscillator (VCO) signal with the local oscillator guadrature signals. The outputs of the third and fourth mixers are applied to the inputs of a difference amplifiers, the output of which controls the frequency of the VCO in an automatic frequency control mode (AFC) to cause the output of the difference amplifier to provide demodulated signal. A switching means operates to alternate the third and fourth signals as applied to the input of the third and fourth means as well as the output as applied to the difference amplifier to cause an additional amplifier coupled to the outputs of the mixers to provide a DC control signal used for automatic gain control.

Baseband demodulator for FM signals

A conferencing apparatus for an FDM communications system employs a first available sideband for communication and a second sideband for signaling. Each subscriber in the system has dual receiving and transmitting equipment which enables a subscriber to communicate with any other subscriber. During such communication, a memory at each subscriber location may receive the frequency pair of one subscriber in a connection. Another subscriber desiring to be conferenced will receive the stored frequency pair from the subscriber who is not on proper frequency. This is implemented by a standby receiver and transmitter associated with each subscriber. Upon receipt of this information, the new subscriber can then tune his equipment to store the frequencies as received to enable the new subscriber to be incorporated in a conference mode. The received frequencies are also stored in the new subscriber memory and hence, any additional subscribers contacting parties to the conference will receive information regarding the elected subscriber who is communicating on his properly assigned frequencies to thereby enable a plurality of new subscribers to join in the conference.

Conferencing apparatus and methods for a frequency division multiplex

An FDM communication system is disclosed wherein two separate intermediate frequencies are utilized in such manner that the difference between transmitting and receiving frequencies thus generated is the difference between the two separate intermediate frequencies, thereby providing the capability of using independent sideband transmission instead of single sideband transmission, thus providing additional channel capacity. A single synthesizer is utilized and a single bandpass filter selects the appropriate upper or lower sidebands of transmission for full duplex operation. One of the two available sidebands is then used for communication, with the other sideband available for signalling, monitoring, break-in or other telecommunication functions.

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Stamford, CT, United States of America

Joseph Reed