| 摘要 |
<p>The variable frequency generator and microphone amplifier supply the variable frequency and speech signals to its line terminals. Two circuits are connected to the line terminals, and to a current source which passes through each circuit a d.c. current of the same intensity; the variable frequency signal is applied to one circuit, and the speech signal to the other. The two circuits are connected to an output circuit, in turn connected to the line terminals and a change-over switch delivers one of the a.c. signals to the output circuit. The d.c. current flowing through the output circuit is not changed by this switching.</p> |
