| 摘要 |
<p>1429514 Television distribution HOCHIKI CORP 14 May 1973 [13 May 1972] 22768/73 Heading H4R In a community antenna television distribution system, each subscriber location 6 includes a generator 8 for alarm signals below the distribution frequency band and transmitted over the distribution network to a receiver 9. The network includes a trunk containing circuits 3 and branches containing circuits 4 which include RCL filters (Figs. 3, 4, not shown) to ensure that only TV signals are available at terminals 23 feeding TV sets 7 and that only alarm signals are available at terminals 24 connected to the generators 8 and the receiver 9 located in a caretaker's room 10. The generators are energized and connected to the network through normally open switches. The circuit 3 nearest the antenna 1 and amplifier 2 includes a capacitor (18) to prevent alarm signals reaching the antenna. The receiver and generators may be two-way, allowing intercommunication between caretaker and subscribers, the alarm frequencies then being unique to respective subscribers. The caretaker may transmit closed circuit programmes and/or a general alarm which automatically applies power to the TV receivers and switches them to the appropriate channel.</p> |
