Abstract: This specification discloses a system comprising a source for selectively applying a test signal to a selected conductor at a first end of a cable and a detector having a plurality of input terminals for connection, respectively, to at least some of the conductors at the second end of the cable. The detector operates to perform individual comparisons of the amplitudes of the signals on its input terminals with the amplitude of a decreasing reference signal and to produce a signal after a predetermined number of such comparisons in excess of a predetermined value have occurred. This last-mentioned signal causes a display unit to indicate the input terminal on which appeared the signal that produced the last comparison in excess of the predetermined value.

Abstract: Disclosed is a recursive circuit capable of serving as a signal detector or as a signal generator. The circuit comprises a shift register capable of storing multilevel signals, and a feedback network responsive to an input signal and to the output signals of selected stages of the shift register. In the feedback network, the output signals of the selected stages are each multiplied by prechosen integers, and then added with the input signal to form a sum signal which is applied to the first stage of the shift register. The sum signal is developed by nonmodulo addition, and the multiplying integers are prechosen to cause the characteristic function of the circuit to be a cyclotomic polynomial. Detection of the presence in the input signal of a signal having a chosen frequency is accomplished by the sum signal excluding a predetermined threshold level.

Abstract: Apparatus and methods are disclosed for detecting a particular gas occurring at any point along a path through a given environment. A tubing having a wall through which the particular gas readily permeates is provided for placement along the path of interest. This tubing is structured so that the particular gas can enter the tubing only by permeating the tubing wall. Detection of the gas and the approximate location of permeation is achieved by withdrawing gases from within the tubing while monitoring both the withdrawn gases and the elapsed time.

Abstract: Disclosed is a circuit for controlling the switching duration of inverting switching devices. The circuit comprises a capacitor connected to the output of the controlled switching device, a resistor connected between the capacitor and a common terminal, and a double Zener diode connected between the switching device's input and the capacitor-resistor junction.

Abstract: Disclosed are signal generators for developing multilevel output signal sequences of a preselected period of repetition. In their general form, the generators comprise a shift register capable of storing multilevel signals, and feedback means. The feedback means multiply the output signal of prescribed shift register stages by selected integers, add the multiplied signals in nonmodulo arithmetic, and apply the added signals to the first stage of the shift register. The multiplying integers within the feedback means are selected to cause the characteristic functions of the signal generator to be a cyclotomic polynomial. For descriptive convenience, the disclosed generator is termed a "cyclotomic circuit." The disclosed cyclotomic circuits are particularly useful in a minimum memory, prescribed-period, signal generator applications. The minimum memory is achieved by separating the prescribed period into power-of-prime factors, and by associating with each factor a cyclotomic circuit.