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In 1608, Dutch eyeglass maker Hans Lipperhey filed the first patent for a working telescope. The patent was denied.
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| Number | Title | Issue Date |
| 7817453 | Thermal foldback for linear fluorescent lamp ballasts A ballast circuit that facilitates providing thermal protection for a fluorescent lamp includes a coupling transformer that couples an inverter circuit to a control circuit. First and second transformer windings in the inverter circuit, and a third transformer windi... | 10/19/2010 |
| 7142081 | Multiple three-phase inductor with a common core An electrical inductor assembly has a plurality of three-phase inductors on a common core. Each inductor includes three coils wound around separate legs of the core. Core bridges extend across the legs to provide an inter-leg path for the magnetic flux produced by e... | 11/28/2006 |
| 7126306 | Motor control unit Windings of each phase in a three-phase AC motor are independent of one another. A motor control unit gives, to windings of each phase (U, V and W-phase), currents (IU, IV, IW) obtained by adding, to a fundamental sine wave current, a current having a frequency whic... | 10/24/2006 |
| 4901213 | Five-legged core type frequency triplo-multiplier A magnetic frequency triplo-multiplier for use as a power source for metal melting furnaces and the like. The frequency triplo-multiplier has Y-connected primary windings that are resonant with each phase of a three-phase alternating-current power source ... | 02/13/1990 |
| 4888525 | Sun tanning apparatus having electronic operating system A sun tanning apparatus has an electronic operating system comprising: (i) a plurality of pairs of fluorescent lamps for providing tanning radiation, each pair of lamps being adapted to be powered from 30 kHz/120 Volt by way of a high-Q series-resonant L-... | 12/19/1989 |
| 4053822 | Subharmonic frequency generator A static electromagnetic frequency changer utilizes linear inductances and capacitances and a saturable reactance to generate subharmonic frequencies. The magnetic components of the circuit are designed to be combined on a single magnetic structure. The f... | 10/11/1977 |
| 4025864 | Direct current modulator for providing variable double frequency electrical power to a load A direct current modulator provides double frequency variable A-C power to a load (such as an induction furnace or induction heater) specifically adapted to operate at the double frequency. The direct current modulator includes a saturable reactor bridge ... | 05/24/1977 |
