Atlantis 32 Channel Manual - Qvis Security

2.7.4 Audio signal outputCommonly the output parameter of a DVR audio signal is greater than 200mv1KΩ(BNC) which can connect a low impedance earphone and active sound boxor other audio output equipments through a power amplifier. If the sound box andthe tone arm can not be isolated, a howling phenomena is often experienced.Here are some methods to deal with this phenomena.1). Adopt a better directional tone arm.2). Adjust the sound box volume to below the threshold that produces thehowling phenomena.3). Use fitment materials that absorb the sound to reduce the reflection of thesound.4). Adjust the layout of the sound box and the tone arm.2.8 Alarm input and output connections1. Alarm inputA. Alarm input is grounding alarm input.B. Alarm input demand is the grounding voltage signal.C. When the alarm is connected with two DVRs or connected with DVRand other equipments, it should be isolated by relay.2. Alarm outputAlarm output can not be connected with high-power load(no more than 1A).When forming the output loop it must prevent the big current from relay damage.Use the contact isolator when there is a high-power load3. PTZ decoder connectionsA. The earth for the PTZ decoder and DVR must be shared otherwisethe common-mode voltage will lead to the PTZ control failure. Shieldedtwisted pair is recommended.B. Avoid high voltage. Take precaution against the thunder and lightning.C. At the outlying end connect a parallel 120Ω resistance to ensure thesignal quality.D. The 485 AB lines of the DVR can not connected with other 485 outputequipment in parallel.E. The voltage between the AB lines of the decoder must be less than 5V.4. Front equipment earthing noteBad earthing can lead to burnout of the chip.5. Alarm input type unlimitedThe DVR alarm output port is constant opening type.11