ELRO FA420DVR 4-ch digital recorder + 500 gb hard disc USERS MANUAL - Manual (Page 11)

Page 11
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Adjust the layouts of pickups and speakers to reduce the occurrence of whistling.
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.Connections to PTZ
A. The PTZ decoder must share a common ground with the DVR or possible presence of
common-mode voltage may cause you to lose control of the PTZ.
We recommend shielded twisted pair cable with its overall shield being used for common
ground;
B. Prevent against high-voltage power surge. Wire cables must be able to protect equipment from
lightning
C. Connect a 120 Ohm resistor in parallel at the far-end to reduce reflection and guarantee the
signal quality;
D. The AB-wire connections of the DVR’s 485 cable cannot be combined with 485 cables from
other output devices;
E. AB line voltage of the decoder should be lower than 5V.
4. Ground Wires of front-end equipment
Incorrect grounding may result in chips being burned.