| 摘要 |
<p>A data transmission system for distributing data signals from a head end 1 to a terminal 2 of the system. An AC signal of fixed frequency is generated 10 at the head end and abrupt changes in amplitude, or notches, are induced 11 in individual cycles of the AC signal, a notch in the first half cycle representing binary "1" and a notch in the second half cycle representing binary "0". The notched AC signal is transmitted to the terminals and the notches are detected 13 to reconstitute the data signal represented by the notches. The AC signal is broken up into a series of bursts separated by DC levels and each terminal is responsive to only the AC burst following a particular DC level. <IMAGE></p> |
