Abstract: A security system comprising a signal-carrying member and a detector for detecting a change in the resistance of the conductive path surrounding a core of the signal-carrying member. The conductive path comprises inner and outer layers of semi-conductive tape separated by an insulating layer but interconnected at one end. The semi-conductive tape of at least the outer layer is made of fibrous material such as carbon-leaded PTFE such that when a sharp object pierces the outer layer and the insulating layer, semi-conductive fibers are dragged from the outer layer into contact with the inner layer and form a conductive bridge between the layers.

Abstract: Apparatus for measuring the phase noise content of a microwave signal source (10) includes a microwave cavity (22) resonant at a fixed frequency, signal generating means (23) operable to generate a frequency representing the difference between the source frequency and that of the resonant cavity, and mixing means (20) for combining the outputs of the source and the signal generating means. The output from the resonant cavity (22) is applied to a phase detector (15) together with a portion of the output of the mixing means (20) and the output of the phase detector (15) represents the phase noise content of the output of the microwave source (10). The signal generating means (23) includes a voltage-controlled oscillator the frequency of which is controlled by an output from the phase detector means (15) so as to maintain the output of the mixing means (20) at the resonant frequency of the microwave cavity (22).

Abstract: A chirp signal generator circuit includes a pulse generator PG for generating a single impulse for application to first surface acoustic wave device SAW. This device produces an output signal comprising several cycles of energy at a predetermined frequency. A threshold circuit TH passes only that part of the output signal which second surface acoustic wave device EXP having the predetermined frequency as its center frequency, and this output signal is then amplified. The second device EXP generates a frequency modulated chirp signal.

Abstract: A gating arrangement for a pulse compression circuit includes a surface acoustic wave delay line SAW responsive to an input pulse to generate a frequency-modulated radio-frequency output signal which is applied to an output gate OG. The output signal is also applied to circuit means DC operable to product a digital pulse corresponding to each cycle of the output signal. The pulses are counted by a counter CT and applied to control means CM. This responds to first and second predetermined counter states to control the operation of the output gate OG.

Abstract: An electrical circuit assembly uses a plurality of stacks upon a generally planar support. Each constituent stack has a plurality of modules having planar substrates extending at right angles to a longitudinal axis of symmetry of the stack. The axis of symmetry is perpendicular to the generally planar support and various electrical interconnections extend between adjacent substrates parallel to this axis. Electrical circuit elements are mounted upon the substrates and the substrates are spaced to facilitate flow of cooling fluid, such as air, between the substrates. Heat conducting fins may be mounted on the substrates. To facilitate flow of cooling fluid, stacks of substrates are staggered or offset from substrates of an adjacent stack. A plurality of the electrical circuit assemblies may be combined together.

Abstract: A temperature-independent gain control circuit includes a dual-gate MOSFET having the input signal applied to one gate and a resistance connected to the source. Control means are provided which are responsive to a control voltage to control the voltage between the other gate of the MOSFET and the end of the resistance remote from the source in such a manner as to maintain the drain current of the MOSFET proportional to the control voltage.

Abstract: An electrical circuit assembly comprises a stack of a plurality of substantially identically constructed modules, each module includes a planar, electrically insulating substrate having constituent elements of a circuit on only one major surface of the substrate, and has an electrically conductive coating on the other major substrate surface. The assembly has at least one conductor member, at least partially, holding the modules in their required locations in the stack, each conductor member and the conductive coatings being interconnected, and together forming an extensive body, to be maintained at zero potential, to reduce electrical interaction between the circuit elements. Each conductor member may be planar in shape, or may comprise a corner piece for the stack. A plurality of stacks on a common support may have a common module, and/or share a common conductor member, and the support may provide a conductor member.

Abstract: Apparatus for controlling the gains of a pair of gain-matched amplifiers includes means for applying a pilot tone of constant amplitude to each amplifier through separate attenuators during a repeated correction time interval. Three control loops are provided, one of which compares the output of one amplifier with a reference signal at times other than a correction time interval to control the gain of that amplifier. A second loop compares the output of the other amplifier with the same reference signal only during each correction time interval to control the gain of the second amplifier. Finally, the third loop compares the output of the first amplifier and the reference signal during each correction time interval to produce a signal controlling the two attenuators.