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...that after Walter Hunt patented the safety pin in 1849, he sold the rights to it for $400?
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| Number | Title | Issue Date |
| 4117412 | Phonograph preamplifier network with infrasonic cutoff response A phonograph preamplifier network with infrasonic cutoff response. In one form, the preamplifier network is a single stage active filter configuration with a high gain, high input impedance differential amplifier provided with an RIAA equalization feedbac... | 09/26/1978 |
| 4105941 | Driver for reactive load An apparatus for driving a reactive load, comprises a plurality of N multnput elements N ࣙ 2, connected in parallel, capable of amplifying a band of frequencies. Two inputs of each element can be connected to sources of direct-current voltage. Each cir... | 08/08/1978 |
| 4099137 | High speed phase lock control for frequency switching A digitally controlled microwave phase lock loop for switching rapidly from one lock frequency to another is disclosed. A digital word corresponding to a desired input voltage for a selected frequency is converted to an analog voltage for application to t... | 07/04/1978 |
| 4087762 | Cable equalization resonant amplifier circuit A cable equalization resonant amplifier circuit for compensating for the signal-attenuation effects of a coaxial cable connected with the amplifier circuit and having a length of up to one-half mile. The gain of the amplifier circuit is matched with the a... | 05/02/1978 |
| 4032855 | Phonograph preamplifier network with infrasonic cutoff response A phonograph preamplifier network with infrasonic cutoff response. The preamplifier network is an active filter configuration with a high gain, high input impedance differential amplifier provided with an RIAA equalization feedback filter network coupled ... | 06/28/1977 |
