Abstract: A method and system for restricting telephone access to a predetermined set of telephone numbers. The method includes comparing the output of a caller ID signal decoder to telephone numbers stored in memory and allowing the telephone call to be completed if there is match between the calling party's number and a number stored in memory. The system consists of connection circuitry to which is connected a caller ID decoder, a number comparator, and an off hook detector. These components interact to restricts calls to only those stored in the number comparator.

Abstract: The present invention relates to battery power system configurations, particularly systems using VRLA batteries in uncontrolled environments wherein the batteries are isolated from the rectifier when the batteries are in the float mode but on line during charge and discharge. The battery power system configuration of the present invention eliminates thermal runaway because the current drawn by each battery is limited to the value determined by a constant current source. A shorted battery cell may be easily detected by observing if the voltage of the battery is lower than a specified and expected value. In addition, battery capacity is maintained by the boost provided periodically from the current source. Finally, batteries are protected against receiving excessive current and since the currents sent through the batteries match the needs of these particular batteries, the life of the batteries is increased.

Abstract: The useful life of an electrolytic battery cell commonly employed in a series string as a backup power source is significantly extended by maintaining the polarization of the positive plates of such a cell at a predetermined level relative to a reference electrode of similar composition in contact with the cell electrolyte. While the cell is being supplied with the usual float charging voltage, a controller circuit senses any variance of polarization below the desired level and meters a minute input current to the positive plates with a resulting increase in the polarization over a substantial time period. The slow biasing of the polarization effects a passivation of the surface of the plates which deters the penetration of oxygen to the plate metal and prevents the deep destructive formation of expansive metal oxide.

Abstract: An integrated circuit contains the gate drivers and the control components for constructing a DC power supply in any of the most popular converter topologies. Multi-function elements in the control circuit minimize the area of the chip. The integrated circuit drives both the upper and lower switches of a half-bridge converter and separately regulates two power supply output voltages, one by pulse width modulation and the other by frequency modulation.

Abstract: A resonant converter feeds five load circuits while maintaining excellent voltage regulation. The power converter features a non-bifilar wound transformer with the resonant capacitors serving the dual function of suppressing diode voltage switching transients while forming the resonant circuit in conjunction with the transformer. Overcurrent circuit protection is also provided.

Abstract: An integrated circuit contains the gate drivers and the control components for constructing a DC power supply in any of the most popular converter topologies. Multi-function elements in the control circuit minimize the area of the chip. The integrated circuit drives both the upper and lower switches of a half-bridge converter and separately regulates two power supply output voltages, one by pulse width modulation and the other by frequency modulation.