| 摘要 |
<p>PURPOSE:To respond to the next callout even if a switch is forgotten to be turned off after the end of monitor, in a 4-line discussion device used as an audio relay device for telephone lines. CONSTITUTION:An audio signal of 4-line inputted from external lines 1, 2 is monitored at a speaker 8 via a coupling transformer/amplifier 6 and amplifier/ transformers 3/4. After the receiver is called out with an audio output of the speaker 8, call is made with a handset 13, the communication voice is detected at a monitor curcuit 23, a relay 24 is activated and a contact 21 is closed and a signal from external lines is applied to the handset, the contact 22 is opened and the sound volume of the speaker 8 is reduced. When the call is finished, no audio signal is applied to a monitor 23 and the relay 24 is restored after the time set to a timer 25, the contacts 21, 22 are restored as shown in Figure to prepare for the next callout.</p> |
