Abstract: The present invention determines the occurrence of leading and trailing es of a target under evaluation by an IFF system. A target's "leading edge" is declared when a predetermined number T.sub.L of correct replies is found to exist in a predetermined group of W.sub.L received replies in response to a number B of interrogations. A target's "trailing edge" is declared when a number T.sub.z of incorrect replies is found to exist in a group of W.sub.z replies if either at least a number B of interrogations have been transmitted after the target's "leading edge" has been declared, or a number T.sub.u of correct replies is found to exist in a group of W.sub.u received replies followed by reduction of this number T.sub.u to a smaller number T.sub.t.

Abstract: A warning is provided when a responding IFF target fails to satisfy friencceptance criteria in response to a given number of cryptographic interrogations. Target position information is utilized to aid in determining whether the responses under evaluation come from the same target.

Abstract: A probabilistic decision making device produces an "Accept" decision when a predetermined ratio of input 1's to 0's is established for a predetermined total amount of binary information. The decision making process in essence is an implementation of probability theory relating to a classical "Urn" problem. The device forms a standard reference decision device for similar types of decision making apparatus.

Abstract: A digital scaler adjusts the processing of an input signal to a digital fback integrator by a multiplying technique which is implemented by shifting the connections between an analog-to-digital converter and the input to an adder, both forming the input section of a digital feedback integrator, in order to maintain a constant dynamic range of the output signal.

Abstract: A Friend-Accept decision is made based upon the accumulated value of only a imited number of responses to interrogations. A correct reply causes the accumulated value to increase by a weighted value U.sub.a, while other than a correct response causes the accumulated value to decrease by a weighted value D.sub.b. A decision to accept as a "friend" occurs when the accumulated value reaches or exceeds a predetermined threshold T.sub.a.

Abstract: A reply simulator for generating binary 1's and 0's representative of "frd" and "non-friend" replies received by an IFF system. Simulated replies are produced in a probabilistic fashion which takes into account variation in a simulated received signal caused by simulated antenna pattern and antenna direction variations, as well as by the probability that a "non-friend" will produce a "friend" reply.

Abstract: Devices exhibiting negative-resistance characteristics are adjusted and irconnected to form a composite device in a manner to permit negative-resistance regions of each device to cooperatively interact to provide additional stable states in excess of the number of stable states exhibited by the composite device not operating in a negative-resistance interactive mode. A minimum number of (M+1)+[(M-1)!] stable states can be achieved by combining M negative-resistance devices to operate in an interactive manner.

Abstract: Frequency and other characteristics of energy contained in a region of the lectromagnetic or acoustic spectrum under examination is determined by subdividing the region, examining each subdivision for energy content, and then further subdividing and examining those subdivisions exceeding a threshold energy. This process is continued until the bandwidth of the last subdivision is equal to the desired frequency resolution.

Abstract: A technique for making IFF Friend-Accept decisions based upon either receng T.sub.a correct replies in any consecutive sequence of W responses in a larger, predetermined number N of responses, or receiving a consecutive series of a predetermined number R.sub.a of correct replies. A Non-Accept indication is provided upon the occurrence of N interrogations before either T.sub.a correct replies are received in the group of W responses, or a consecutive series of R.sub.a correct replies are received. Target leading edge information is also derived from these determinations.

Abstract: A technique for testing decision-making devices of the Yes-No, or friend ept type in order to determine their operating performance characteristics. Binary information having predetermined characteristics is applied to a device under test, and response by the device observed.

Abstract: A technique for detecting and eliminating "sea-spike" interference in a rrn radar-signal. A series of signal delay means in cooperation with associated subtractors are utilized to detect particular sea-spike modulation interference frequencies. Detection of these modulation frequency components causes activation of means for preventing the sea-spike contaminated return signal from being further processed.

Abstract: A range-determining circuit which counts the time from the transmission of detection-signal to its echo return, in units corresponding directly to the distance that the detection signal travels.

Abstract: Detection of a class of input-signal pulse-sequences is accomplished by carison of the signal as sampled and digitally coded twice per pulse-width with a similarly sampled reference signal also digitally coded, but having an arbitrary complementary digital pair in pulse positions whose information content is of no concern.

Abstract: A biased sequence of binary bits is produced such that the probability that any randomly selected bit will be a "1" is equal to a preselected desired number.

Abstract: Rotation of a search radar antenna primary focusing structure about both elevation and optical axes provides stabilization of the radiated beam in both level and cross-level respectively.

Abstract: Measurement of the range of a detected target is accomplished through utiation of a large bistatic-angle radar system having two transmitters used in conjunction with a receiver indicating the duration of received target forward-scattered signals from each transmitter.