| 摘要 |
<p>PURPOSE: To disable the separation of teletext information by controlling control inputs to two change-over switches by an output from a logic circuit and connecting each 1st input to an output by a binary level under a specific condition. CONSTITUTION: The switching of a 1st code inverter w1 is delayed by the two- clock period of a signal x0, i.e., the switching is accurately generated at a moment when the digital word x0 to be supplied to an input e1 appears on the output of a delay element vg. A logic circuit gc generates a binary level for connecting the 1st inputs of the change-over switch u1, u2 to respective outputs when signals based on the shown expression I appear on five inputs e1 to e5 from its output. In this case, '0' and '1' are two binary levels and 'x' indicates the appearance of either one of the two binary levels. Consequently the separation of teletext information can not be separated.</p> |
