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US 3,938,142 AGranted
Ultrasonic transmitter for the remote control of radio and television receivers
AssigneeInternational Standard Electric Corporation
InventorWolfgang Schroder
Life of this patent
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Abstract
A polarizing D.C. voltage is generated at the capacitance of the ultrasonic transducer and then short-circuited by a parallel-arranged electronic switch controlled by the command signal frequency to be radiated. A direct current stored in an inductance during this short-circuit phase is supplied via a decoupling diode to the electrodes of the ultrasonic transducer upon opening of the switch, and after having been transformed into a voltage. The polarizing D.C. voltage is thus re-generated periodically.
Claims9
An ultrasonic frequency transmitter for remote control devices, comprising:
- an electrostatic transducer;
- a source of d.c. voltage connected in parallel with the electrostatic transducer;
- a controllable electronic switch connected across said electrostatic transducer for periodically shorting said transducer;
- and
- an a.c. voltage generator connected to said electronic switch for controlling said switch so that said transducer transmits a desired ultrasonic frequency.
2 more elements
Dependencies are inferred from the claim text.