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DVR Alarm Output Setup | Viewtron CCTV Surveillance DVRs

CCTV DVR Alarm OutputViewtron surveillance DVRs have alarm output ports that support the ability to connect external devices such as sirens and strobe lights. The alarm outputs on the DVR can be configured to be triggered by an event, such as camera motion detection or door contact via an alarm input. Each alarm output of the DVR is a simple relay circuit that switches from one position to the other (from normally closed to normally opened).

Most Viewtron CCTV and HD-SDI DVRs have 4 alarm outputs on a terminal block on the back of the DVR case. Please check the specification for the model that you are interested or contact a sales engineer at CCTV Camera Pros to confirm how many alarm output ports your DVR has. The setup guide below will walk users through how to setup alarm outputs on a Viewtron DVR.

NEW! Recommended DVRs

Please note that HD-SDI Viewtron DVRs have been discontinued. We highly recommend our iDVR-PRO surveillance DVRs. iDVR-PRO has outstanding support for alarm input / output integration. You can see how to setup alarm inputs on your DVR here, and how to setup alarm outputs on your DVR here.

DVR Alarm Output Overview

The alarm output ports on the back of the DVR are each labeled with NO C NC. The NO stands for normally opened, NC means normally closed, and C means common contact. When the alarm is in the non-triggered state, it is normally closed which means that the circuit is allowing current to flow from C to NC. When the alarm is triggered, the relay is enabled and switched from the normally closed (NC) to normally opened (NO) position.

The security application used in these instructions uses a 12v DC powered strobe light. The goal is to turn the strobe light on when an alarm is triggered. For this application, we will use a door contact connected to the alarm input of the DVR to trigger the output.

Please note that the DC transformer used to power the strobe light / siren is only used to power the siren and has nothing to do with the power supply of the DVR. The concept is that the strobe light sits dormant / un-powered (relay in the NC position) until the alarm goes off. When the alarm goes off, the relay is enabled and allows power to flow to the strobe light (via switching the power of the circuit to the NO position), which turns it on.

WARNING: DVR alarm outputs / relays have a maximum power rating. The alarm outputs of Viewtron DVRs have a maximum power rating of 2A 120VAC, 2A 24VDC. This rating should accommodate almost all standard burglar alarm equipment, but you should check the specification of each device to be sure.

If you are using these setup instructions to guide you on integrating alarm devices on other types of surveillance DVRs (not Viewtron), is strongly recommended that you consult the manual of your DVR to understand the maximum power that your DVR alarm outputs can use. Using an alarm device that draws more power than the relays of your DVR are rated at will cause damage to the relay terminals and / or can ruin the entire DVR.

DVR Alarm Output Wiring

The siren in this example uses a 12v DC power supply. These typically have a single 3.5mm plug on the end of the cable. If your DC transformer has a single plug (instead of separate positive and negative wires), you can use a PT-4 pigtail power lead to convert the plug to separate positive and negative wires.

  1. Connect the positive wire from the power supply to the NO terminal of the alarm-out port.
  2. Connect the negative wire from the power supply to the negative cable of your output device (in this case a strobe light).
  3. Connect the positive wire from the strobe light to the C terminal of the alarm-out port.

    DVR Alarm Output Wiring Diagram

DVR Alarm Output Configuration

In this example, we will use the input from a door sensor to trigger the alarm output (with strobe light connected to it). Please read these setup instructions for details about how the alarm input was configured for the door sensor.

Follows these instructions to configure the door sensor to trigger the alarm output.
  1. Access the advanced setup of the DVR the clicking on the Home button, then select Setup > Advanced.

  2. On the Advanced menu, click on the Event tab, then click on the Sensor button.

    DVR Alarm Input Configuration
  3. On the sensor screen, you can choose the action(s) that you want taken. To set up the strobe light on alarm output one to be triggered, click on the gear icon in the alarm section of the sensor action settings. This will open a sub-window that will let you choose to enable all alarm outputs or select the specific ones that you want to be triggered.

    Alarm Output DVR Setup
  4. Click OK, then OK again to save the settings.
The alarm output of your DVR is now set up. When the door contact is opened, the strobe light will turn on.


These setup instructions were written by , co-founder and managing partner of CCTV Camera Pros. Please send questions to or post on our support forum.