| 摘要 |
<p>A communication system uses a continuous tone selection system and a decoding unit (18) to identify and pass signals containing a unique continuous tone and to block signals not containing that unique tone, the receiver being individualised to that unique tone by interrupting a selection from a plurality of interruptable links (35), and each link passing (or blocking if interrupted) a control input to the decoding unit and is characterised by a free-running multivibrator (52) injecting a second set of control inputs onto the links (35) so that the decoding unit hunts between looking for one unique tone and at least one other unique tone and in that the multivibrator is stopped when the decoding unit passes a signal so that signal continues to be passed.</p> |
