Abstract: A battery charging circuit is disclosed which rapidly charges a battery from some level of discharge, including fully discharged, to fully charged without endangering the battery. The charging circuit includes a control circuit which provides switching type regulation responsive to current, voltage and temperature signals from the battery, and also a timer circuit for automatically halting the charging current to a defective battery. The control circuit receives a temperature compensated voltage signal (TCVS) which is useful for effectively implementing a charging program which includes a low constant current mode, a high constant current mode, and a constant voltage mode. The TCVS is generated by connecting a thermistor responsive to battery temperature in parallel with one resistor of a resistive voltage divider network which is connected across the battery terminals.

Abstract: In a seismic exploration system wherein a plurality of geophones are utilized to detect seismic waves and transduce the detected seismic waves into representative electrical signals, method and apparatus is provided whereby a plurality of remotely located geophones can be tested from a central location to determine if the remotely located geophones are operable. Leakage tests, continuity tests and levitate tests are performed on the plurality of remotely located geophones and the results of these tests are transmitted to a central location.

Abstract: An optical absorbance detector which can be used in process chromatographic analyzers is provided. Improvements are provided in noise reduction, temperature stability, operator convenience and construction. Noise reducing features include electrical signal filtering and optical system alignment. Temperature stability features include an electronic preamplifier inside the oven and a temperature controller to maintain an integrated circuit at a constant temperature. Operator conveniences include built-in calibration for electronic circuits and easy optical filter replacement. Construction features include explosion resistance and small size.