| 摘要 |
<p>A signal transmission system comprises a transmitter arranged to transmit a coded signal as a series of pulses of line of sight radiation having a predetermined minimum interval therebetween, a receiver responsive to such radiated pulses received at a corresponding minimum interval, and a plurality of repeater devices. Each repeater device comprises a radiation receiving element, a radiation transmitting element, and means responsive to receipt of a pulse of transmitted energy by said receiving element for causing said transmitting element to emit a corresponding pulse of transmitted energy and for causing said receiving element to be disabled for a predetermined period of time corresponding to at least a multiple of the duration of the pulse transmitted by said transmitting element. A plurality of the repeater devices can thus be arrayed between said transmitter and receiver to provide a plurality of line of sight radiation propagation paths with a plurality of repeaters each in line of sight of the transmitter and/or other repeaters and with the receiver in line of sight of a plurality of said repeaters so that random interruption of the signal propagation paths does not interrupt the transmitted signal. Each repeater may comprise its own transmitter and keypad to provide an audience polling system.</p> |
