Abstract: Speaker verification is performed by converting a spectral analysis of an input speech signal into a digital format. This digital format is sent directly to the address input of memory storage defining the address which contains relevant information pertaining to the actual speech spectrum. After training, each address contains labels defining whether the address is not used, is used by multiple users, or is used by a single user. Actual verification is performed by counting each occurrence of a valid user address during speech input by a speaker and selecting the highest count as indicative of the user who was speaking.

Abstract: A fourth (or higher) order filter has a series resonant section terminated by a parallel resonant section, both based on frequency dependent negative resistance (FDNR). The FDNR, resistance and capacitance (representing damping) of the series section are provided by a capacitive potential divider (C41,C42) connected between low impedance input (A) to the filter and an intermediate terminal forming the input of a unity-gain amplifier (A4) whose output is connected via a resistance (R4O) to the tapping point of the divider; the intermediate terminal is connected via a second resistance (R1) to the parallel section.

Abstract: A filter network that exhibits a bandstop response comprises a network of basically low pass or high pass structure. The network is developed by choosing a bandstop transfer function, a fourth-orderelliptic is disclosed, which is converted to a low pass function. This function describes a passive low pass LC ladder network including a negative impedance element. A Bruton transformation is applied to the passive LC network to give an active version including an ungrounded negative resistance network in a series arm and frequency-dependent negative resistances in shunt arms without requiring inductance coils for its implementation.

Abstract: An equalizer network that exhibits stability and may be cascaded with a transmission channel is disclosed. The network includes only two operational amplifiers, resistors and capacitors and provides a bump shaped amplitude characteristic at resonance frequency. The equalizer may be modified to exhibit selectively a `bump` or `dip` at resonance, and may be so constructed that trimming operations and the independent selection of parameters is facilitated.

Abstract: A construction of an active filter having the same characteristics as a predetermined passive filter is described in which the capacitors of the passive filters are replaced by a topologically equivalent first network of resistors and the inductors of the passive network are replaced by a topologically equivalent second network of resistors, the two networks of the resistors being interconnected in a manner corresponding to the connections in the passive filter and connected to points corresponding to interconnection points of the passive filter by means of negative impedance converters, the converters connected to the first network having conversion ratios effective to convert resistance into negative capacitance and the converters connected to the second network having conversion ratios effective to convert resistance into negative inductance. The input and output to the active filter may be through similar negative impedance converters or may be directly to points in one or other resistive networks.