Q-See QSD6204 - Manual (Page 13)

D. Alarm Installation
The DVR has an internal switch for sounding an alarm. The switch is normally
open, but when the sensor is triggered, the alarm is activated as well. The
circuitry is as follows:
There are two steps for alarm installation.
(a)
Connect the alarm power lines to the alarm switch terminal.
(b)
Connect the alarm power lines to the appropriate power source.
The following diagram shows how you install an alarm device into your
DVR.
-10-