7" 4K HDMI/3G-SDI On-Camera Tally Field Monitor (V2) - Ikan
Amazon.com : AVMATRIX TS3019 Wireless Multi-Camera Tally System 433Mhz 200m Distance Wireless and Wired Tally Connection Support Remote PTZ Camera Control via RS-232/RS-485 : Electronics
Blackmagic Forum • View topic - How to show an active camera