Abstract: An active acoustic intrusion detection system includes a pair of dipole emitters (180 degrees out of phase with each other) which emit an audible frequency f (preferably 1 KHz) and a pair of detectors preferably mounted ¼ wavelength (3 inches) apart in the (non-echoic) nulls of the emitters. The detectors (microphones) spatially sample a stationary wave which is generated by the emitters (speakers). The output of each microphone is fed to an ADC and the digital output of the two ADCs is used to generate a four dimensional vector. At startup, a reference vector is determined and stored. During operation, vectors are sampled, filtered, smoothed and averaged periodically. When an average vector deviates from the reference vector by a set amount, an alarm is generated.

Abstract: An active acoustic intrusion detection system includes a pair of dipole emitters (180 degrees out of phase with each other) which emit an audible frequency f (preferably 1 KHz) and a pair of detectors preferably mounted ¼ wavelength (3 inches) apart in the (non-echoic) nulls of the emitters. The detectors (microphones) spatially sample a stationary wave which is generated by the emitters (speakers). The output of each microphone is fed to an ADC and the digital output of the two ADCs is used to generate a four dimensional vector. At startup, a reference vector is determined and stored. During operation, vectors are sampled, filtered, smoothed and averaged periodically. When an average vector deviates from the reference vector by a set amount, an alarm is generated.

Abstract: An inductor element comprises a copper pattern on a PCB on which a magnetic powder is deposited. The inductor is formed according to the method of the invention by etching a copper layer of a PCB in a desired pattern. A magnetic powder-loaded ink is then screened or stenciled over the pattern of the inductor elements etched in the copper layer of the PCB. The resulting inductor element is enhanced, having increased low frequency inductance and increased high frequency loss. Multiple inductor elements may be formed on a single PCB in a single process without requiring further cost or steps in the method.

Abstract: An LED array circuit includes a number of series connected LED pairs, each pair including two parallel connected oppositely polarized LEDS. The array is coupled to a standard AC voltage source in series with an inductor L having Q>5 and a reactance which is equivalent to the resistance of a current limiting resistor. The use of an inductor in place of a resistor increases the efficiency of the array to approximately 80%. The efficiency of the array is increased even further by coupling a capacitor parallel to the array and by tuning the inductor and capacitor to the frequency of the AC voltage source. According to one embodiment of the invention, a somg;e retro-fittable unit is provided wherein an inductor, a capacitor, and an array of LEDs are contained in a housing having substantially the same size and shape as a standard incandescent bulb or the lens/filter used in a traffic signal display.

Abstract: A high speed synchronous digital bidirectional data bus system is provided and includes an M-bit unterminated data bus, an unterminated standing sine wave clock bus, and a plurality of integrated circuit bus interfaces. Each IC bus interface is preferably substantially incorporated on a single CMOS LSI chip and includes M bus drivers with associated send data logic, M data receivers with associated receive data logic, and a clock receiver. The output currents of the bus drivers on all of the chips are preferably stabilized so that each driver drives the bus at substantially the same output current. The drivers are preferably complementary polar driven CMOS logic elements. For this case, for each data receiver, a bus keeper is coupled to the output and the input of the bus receiver to maintain the last state of the data bus. In addition, the clock receivers and the data receivers are embodied as high speed comparators having internal hysteresis.

Abstract: An isolated, high impedance, DC current source is provided from a readily available AC type source. The DC current source includes an isolating transformer which receives the AC source signal and provides an isolated AC voltage signal therefrom, a resonant low pass filter which is tuned to the frequency of the AC type source and which takes the AC isolated voltage signal and generates therefrom an AC current source signal, and a rectifier which rectifies the AC current source signal to provide a DC current source signal. A voltage limiting clamp is preferably coupled to the rectifier in order to limit the output voltage to a desired level. The resonant low pass filter is preferably comprised of two substantially equally valued inductors coupled to respective poles of the secondary winding of the isolating transformer, and a capacitor which is coupled to both of the inductors.

Abstract: A clock phase and frequency distribution system is disclosed which uses a standing sine wave and provides substantially simultaneous significant crossing instances everywhere in the system while using low power and not requiring bus termination or precise control of transmission path characteristics (Z.sub.0). The system is particularly advantageous in high frequency applications such as digital, linear (non-branched), backplane applications, but is also applicable to other topographies such as stars, rings, and meshes. The system includes a sine wave generating and driving circuit, a clock bus, and clock receivers. The clock receivers present a high impedance interface to the clock bus.

Abstract: Output characteristics of CMOS chips are controlled by providing a known and stable current to a representative transistor of known relative size in the CMOS chip, and arranging the output CMOS driving transistor(s) of the chip, which are of known size relative to the representative transistor, in current mirror relationship with the representative transistor. Two primary embodiments of the invention are provided. In a first primary embodiment (I.sub.d,SAT stabilization), the representative transistor is a diode-connected transistor with a saturation current which is generated by the current source and which is also provided to drive the output transistor device(s) when it is ON. In the second primary embodiment (R.sub.ON stabilization), instead of being diode-connected, a servo is used to adjust the gate voltage of the representative device until it is greater than the drain voltage by a desired amount. In this manner, the resistance (R.sub.

Abstract: A connector system having an electrical switch capability for connecting a first electrical conductor to a second electrical conductor is provided and includes a spring biased contact element having a first portion for making electrical contact with the first electrical conductor, a second tapered contact portion for mating with a conductive rim of a hole of the second conductor, and a spring portion for biasing the tapered contact portion in the closed position where the second tapered contact portion mates with the conductive rim, and an actuation member for bringing the tapered contact portion into the open position. The actuation member may be a plunger or the like which enters the hole with which the tapered contact portion is mated from the rear side and pushes the tapered contact portion out of contact.