| 摘要 |
The present invention features an electronic fluorescent lighting ballast which provides a way to transmit data by modulating the light that is emitted from lamps in a luminaire. The modulation occurs at a sufficiently high frequency, so that it is imperceptible in the range of human vision. Data can be represented in the emitted light by frequency-, phase- or amplitude-modulation. Communication methods can be either simplex or duplex. In the preferred embodiment, a simple modification of the base circuit of a typical, Class D, bipolar, push-pull inverter permits frequency- or phase-modulation of the inverter waveform. This causes modulation of the emitted light from the lamps of the luminaire. The transmission of data through an otherwise conventional lighting luminaire is desirable for many commercial applications. One example of its usage is in the transmission of audio or digital information in a grocery or department store from a centralized computer to display units on store shelves. Another example of its usage is in the transmission of audio or digital information from a central computer to various fixed or portable display terminals in an airport, providing arrival and departure information.
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