| 摘要 |
<p>The subscriber"s station comprises a base apparatus (1) and a wireless portable apparatus (2) between which a transmission is provided by means of short pulses PPM or PCM in the range of infrared radiation, optionally by means of a relay station (17) fixed to the ceiling. To this effect, there are provided transmitters (4, 7) and receivers (5, 8) of infrared pulses. For a PPM transmission there are provided BF/PPM and PPM/BF converters (18, 22; 19, 24) and for a PCM transmission there are provided a PCM-NRZ/PCM-RZ converter (34), a PCM-RZ/BF converter (37), a BF/PCM-RZ converter (35) and a PCM-RZ/PCM-NRZ (32) for which NRZ means "non-return to zero" and RZ means "return to zero". The use of a modulation mode with discreet values and short pulses only requires a low transmission power. </p> |
