Hooking up my normal 16VAC door bell up directly to my Dahua NVR, this method requires access to just some portion of your doorbell wiring.. I am tapping into mine in the basement, because the transformer is attached to my furnace and the wiring is easiest to access there, and its also close to my NVR location. goal: keep PTZ parked on driveway unless someone is at the door, then change to preset to get a better view. video demo: Hardware Used: Elk ELK-930 Doorbell and Phone Ring Detector (only need one db module, you'll have a spare tp and db module) Seco-Larm SA-025Q Enforcer Multi-Purpose Programmable Timer Module 12v Barrel Plug Splitter - This is inline w/my NVR PSU and one leg is cut off and hardwired into Timer Module Dahua 4216-4k NVR, but should work on most hardware NVR w/IO inputs I would hope. Dahua Mini Black face PTZ - you probably want a ptz thats fairly quick. The wiring is pretty straight forward, I stripped back the jacket over my power cables going up to the wall mounted doorbell.. took one of the two lines, dont matter what one as long as its hooked to the doorbell transformer, then cut and stripped it.. then you put the module in place inline. It detects current passing through and does not need to be directly connected to the actual doorbell switch in any way.. which is really convenient, and its compatible with lighted doorbells. Now it would have been great if I could have just hooked that right into my NVR, but that unfortunately wont work.. the momentary tap of your doorbell is unlikely to last long enough for a reliable trigger.. if you hook it up like this it will work if you hold down the button for a second or so.. but you might try it, I bet a digital doorbell ringer that played audio would energize more than long enough unlike my bell striker.. I've been thinking of a westminster multi-tone unit one day, tha'd be nice. so thats where the timer module comes in, it takes that momentary split second switch and turns it into a longer alarm.. which is what we need to catch those delivery people who just drop, tap and run. Set the dips on the timer module as: 1 - ON 2 - OFF 3 - ON 4 - ON 5 - OFF 6 - OFF Wiring as follows: TRG : Elk Doorbell Sensor Signal Line (w/pull up resistor installed) - : To 12v Black on cut/stripped splitter end. +: To 12v Red on cut/stripped splitter end. NO : Alarm Input on NVR COM : Ground Output on NVR, Ground Input to Elk Doorbell Sensor NVR Configuration screenshots attached below, Tour will change the camera display on the NVR its self.. so when the doorbell rings the grid will switch to a single view of just the front door until the alarm has ended (anti-dither), I'll post a video of it in action later. tip: use that grounding screw on back of chassis to provide NVR w/proper ground when you start hooking up alarm inputs.