DVR User Manual
10
2-6-3 Audio signal input
Audio port is BNC connection.
The input impedance is high so the tone arm must be active.
The audio signal line should be firm and away from the electro magnetic Interference and connected
credible which avoid false and joint welding and oxidation. The high voltage current should be
avoided especially.
2-6-4 Audio signal output
Commonly the output parameter of DVR audio signal is greater than 200mv 1KΩ (BNC) which can
connect the low impedance earphone and active sound box or other audio output equipments
through power amplifier. If the sound box and the tone arm cannot be isolated, howling phenomena
is often observed. There are some methods to deal with the above phenomena.
1. Adopt better directional tone arm.
2. Adjust the sound box volume to be under the threshold that produces the howling
phenomena.
3. Use fitment materials that absorb the sound to reduce reflection of the sound.
4. Adjust the layout of the sound box and the tone arm.
2-6-5 PTZ decoder connections
1. The grounding of the PTZ decoder and DVR must be shared otherwise the common-mode
voltage will lead to the PTZ control failure. The shielded twisted pair is recommended.
2. Avoid the entrance of high voltage. Make the layout. Take precaution from the thunder.
3. In the outlying end connect 120Ω resistance paralleled to reduce the inflection and insure
the signal quality.
4. The 485 AB lines of DVR cannot connect with other 485 output equipments paralleled.
5. The voltage between the AB lines of the decoder must be less than 5V.
2-6-6 Front equipment grounding note
Bad grounding can lead to the burnout of the chip.
