| 摘要 |
<p>Transmitter station 1 has a data source, a crypto unit 4, a buffer store 5 for encrypted signals and a transmitter 6 with an aerial 7, all with a common power supply 8. A switching control unit 9 has a position in which it connects data source 3 and crypto unit 4 to the power supply 8 but isolates transmitter 6 therefrom, and another switch position in which transmitter 6 is connected to the power supply 8 while data source 3 and crypto unit 4 are isolated therefrom. In this way, if any signals output from data source 3 pass directly (i.e. not via crypto unit 4) to the input of transmitter 6, they will not be sent on into the network because transmitter 6 is "off" (i.e. de-energised) at that time. </p> |
