Vacron VDH-NK300, Руководство по оборудованию

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VDH-NK300 Hardware Manual
8
Voice input impedance is high, so the microphone must be a microphone
connected to the power supply.
Like video input, voice transmission cables should avoid interference, fake,
poor contact, and special attention to prevent the current of the
high-voltage.

Audio Output
The audio output parameters of NVR are generally greater than 200mv 1KΩ
(BNC), you can directly connect to the low impedance headphones, powered
speakers or other sound devices through a power amplifier.
When the external speakers and microphones can not achieve spatial
segregation, it is prone to the phenomenon of whistling.
You may adopt the following actions,
1.
Using better directional microphones
2. Adjust the speaker volume to make it lower than the value of the
generated howling.
3. Using sound-absorbing materials for decoration to reduce sound
reflections and improve the acoustic environment;
4. Adjusting the layout of the microphone and speakers can reduce the
whistling.

AlarmIn/AlarmOut connections
Pay attention to the following before installation.
1.
AlarmIn
(a)
Alarm input is grounding alarm input
(b) The alarm input signals require voltage signals to the ground
(c) When the alarm device is shared with two NVRs or connected to a
NVR and other devices, it should be isolated by relays.
2. Alarm OUT
The alarm output of the NVR can not be connected with high-power
load (no more than 1A). In the output circuit, be careful about the
excessive current that may cause damage to the relay. When using
high-power load, extra relays are needed.