Abstract: A method (300) and apparatus (200) are provided for operating a portable pager. The method and apparatus eliminate channel noise between paging tones and voice messages. Channel noise is squelched between paging tones and voice messages using a delayed N timer, thereby allowing the speaker to remain on. Paging tones are received and played at the speaker during a signaling squelch mode of operation. The detection of the paging tones and subsequent drop in carrier signal, initiates a timer during which channel noise is squelched during a carrier squelch mode of operation. The timer is delayed (delay N timer) so as to expire only after the carrier frequency is re-established. Once the carrier signal is re-established followed by the delayed timer expiration, the carrier squelch is removed. The speaker remains on during both signaling squelch and carrier squelch. Hence, paging tones are heard, channel noise is silenced, and then voice messages are played.

Abstract: A method (300) and apparatus (200) are provided for operating a portable pager. The method and apparatus eliminate channel noise between paging tones and voice messages. Channel noise is squelched between paging tones and voice messages using a delayed N timer, thereby allowing the speaker to remain on. Paging tones are received and played at the speaker during a signaling squelch mode of operation. The detection of the paging tones and subsequent drop in carrier signal, initiates a timer during which channel noise is squelched during a carrier squelch mode of operation. The timer is delayed (delay N timer) so as to expire only after the carrier frequency is re-established. Once the carrier signal is re-established followed by the delayed timer expiration, the carrier squelch is removed. The speaker remains on during both signaling squelch and carrier squelch. Hence, paging tones are heard, channel noise is silenced, and then voice messages are played.

Abstract: A thermal conductivity detector (TCD) includes a detector cell body having a plurality of fluid cavities, at least one detector element associated with each of the plurality of fluid cavities, and a control circuit associated with each of the at least one detector elements, wherein the control circuit varies the power to the at least one detector element to maintain the at least one detector element at a constant temperature. Power compensation and temperature compensation are also provided to minimize temperature variation of the body of the TCD cell.

Abstract: Methods and apparatus for collecting gasses from the sample headspace of a sealed sample container are disclosed. The gasses in the sample headspace are withdrawn by inserting a probe into the sample headspace and permitting the gasses to flow into an external headspace. The probe is then disconnected from the sample to seal the external headspace and the external headspace is then connected to an analytical instrument such as a gas chromatograph to permit the sample gasses to be transferred out of the external headspace and into the instrument. The step of transferring the gasses is preferably accomplished by connecting a source of carrier gas to an inlet port of the external headspace and sweeping the sample gasses from the external headspace.

Abstract: Methods and apparatus for extracting sample components from complex matrices using supercritical fluid as the principal extracting solvent are disclosed. The invention takes advantage of the fact that the solvent power of a supercritical fluid is stepwise settable by the parameters of density, modifier concentration, and temperature. Accordingly, methods and apparatus for extracting a component from a sample using fluid flow system having a variable and controllable flow restriction are disclosed. The methods of the present invention comprise the steps of inserting the sample into the sample container section, inputting temperature, pressure, flow rate and extraction time set points. Flow rate is controlled and system pressure regulated by the variable flow restriction. The output stream from the extraction is then expanded through a nozzle and into a trap. In certain embodiments, the trap is filled with chemically active packing material.

Abstract: Methods and apparatus for extracting sample components from complex matrices using supercritical fluid as the principal extracting solvent are disclosed. The invention takes advantage of the fact that the solvent power of a supercritical fluid is stepwise settable by the parameters of density, modifier concentration, and temperature. Accordingly, methods and apparatus for extracting a component from a sample using fluid flow system having a variable and controllable flow restriction are disclosed. The methods of the present invention comprise the steps of inserting the sample into the sample container section, inputting temperature, pressure, flow rate and extraction time set points. Flow rate is controlled and system pressure regulated by the variable flow restriction. The output stream from the extraction is then expanded through a nozzle and into a trap. In certain embodiments, the trap is filled with chemically active packing material.

Abstract: Methods and apparatus for extracting sample components from complex matrices using supercritical carbon dioxide as the principal extracting solvent are disclosed. The present invention takes advantage of the fact that the solvent power of a supercritical fluid is stepwise settable by the parameters of density, modifier concentration, and temperature. Accordingly, methods and apparatus for extracting a component from a sample using flow system having a variable and controllable flow restriction are disclosed. The methods of the present invention comprise the steps of inserting the sample into the sample container section, inputting temperature, pressure, flow rate and extraction time setpoints. The flow rate is controlled and the system pressure regulated by the variable flow restriction.

Abstract: Methods and apparatus for extracting sample components from complex matrices using supercritical fluid as the principal extracting solvent are disclosed. The invention takes advantage of the fact that the solvent power of a supercritical fluid is stepwise settable by the parameters of density, modifier concentration, and temperature. Accordingly, methods and apparatus for extracting a component from a sample using fluid flow system having a variable and controllable flow restriction are disclosed. The methods of the present invention comprise the steps of inserting the sample into the sample container section, inputting temperature, pressure, flow rate and extraction time set points. Flow rate is controlled and system pressure regulated by the variable flow restriction.

Abstract: The bar code on the cylindrical surface of an object is accurately read by rotating the object past a bar code reader so that the bar code passes the reader a plurality of times. Each of the readings from the reader is compared with the other readings and a final reading is provided when several of the same readings is obtained in succession. The object may be rotated pass the reader first in one direction and then in the opposite direction to assure a proper reading in the event that the bar code is backwards. Also, the object may be rotated at a varying speed to obtain the optimum scan speed for the particular density of the bar code.

Abstract: An analog-to-digital converter system is disclosed in which the amplitude of the signal is compressed by means including a logging means prior to an analog-to-digital converter. Reference signals of known values are applied to the logging means and their values at the output of the converter are used to determine a linearity factor which is applied to a multiplier coupled to the output of the converter. The amplitude of one of the reference signals at the output of the multiplier is compared with what it should be and the difference is added by an adder at the output of the multiplier.

Abstract: The linear component appearing in the output of two logarithmic amplifiers connected for temperature compensation and having matched feedback semiconductor devices is cancelled in a resistor connected in series with a logarithmic device between the output and a point of reference potential so that a purely logarithmic voltage appears at their junction.