Syscom 421s configuration requires accessories below:(SONY/Panasonic/Datavideo)
- USB TALLY switching box
- Customized TALLY cable(According to the brand of video switcher)
- 4 TALLY lights

About BMD Switcher:

Syscom 421s configuration requires accessories below:(SONY/Panasonic/Datavideo)
About BMD Switcher: