dvr firmware which can support RS-485 port, View dvr firmware, Sunivision Product Details from Sunivision Technology Development Co., Ltd. on Alibaba.com
RS-232 (serial) to RS-485 adapter for PTZ Camera control
Ahd Camera System Rs485 Communication Joystick 3kd For Hikvision Dahua Dvr 3d Analog Cctv Dome Ptz Keyboard Controller - Dvr - AliExpress
KKMOON H.265+ 4/8/16CH 5IN1 1080P DVR Video Recorder For CCTV Camera System B7G3 | eBay
How to connect multiple PTZ cameras with RS485 to one DVR - YouTube