| 摘要 |
At each booth there is, at an elevated position, an infra-red transmitter. The infra-red serves as a carrier for multiple audio messages. The audio messages are in various languages, and each language has a supplementary message of greater detail. The attendee carries an infra-red receiver, from which he selects whatever language he desires. He also has a button which, when he chooses, brings in a supplementary message in the same language. The attendee points his receiver towards the booth of interest. Thus he chooses the booth and generally neighboring booths do not interfere, as they would with radio frequency transmission. The receiver may be hand held, held next to the ear, badge level mounted, or head mounted. To reduce the time an attendee has to wait before his message starts, identical broadcasts are made cyclically at differing time intervals, and the system automatically picks the time slot most suitable for starting a message at the beginning, so only minimum time is consumed waiting for the start. The transmitting beam width, and the receiver capture angles, are adjustable to reject cross-talk between neighboring transmitting and receiving stations.
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