Grandstream Surveillance Buyer's Guide - Manual (Page 27)

Integration with IP Encoders/Decoders
Like Grandstream’s cameras, the GXV3504 and GXV3500 offer audio
inputs/outputs as well as alarm inputs/outputs to integrate with
existing sirens, alarms, intercoms, speakers, microphones, etc. Like
the cameras, simply connect the devices to utilize to the GXV3504 or
GXV3500, then login to the product’s web user interface to tell the
device what to do when an alarm is triggered.
Integration with the GVR3550
The GVR3550 are able to support these devices when connected
directly to a camera or encoder/decoder that is being recorded/mon-
itored by the GVR3550, but they can also be integrated/connected
directly to the GVR3550 using the ports on the back of the device.
This makes the GVR3550 a great option for security offices/security
guards as they can simply integrate their existing intercom system
with the GVR3550 by plugging it into the back of the GVR3550 right
there in the security office. Many dedicated security offices have all
of the alarms, sirens and intercoms routed back to the security of-
fice, in which case all you have to do is connect those devices to the
back of the GVR3550.