Hi Tanis,
Your existing Multibridge SD should be fine for what you need to do but it is not a video router or switcher and the SDI inputs and outputs are not (currently) designed to select between two different devices as a router would do.
When working with a Digibeta, connect the DeckLink Plus card directly to the SDI input and output of the Digibeta. If you want analog monitoring then you can either use the analog outputs of the Digibeta or else connect the Multibridge SD, to a spare SDI ouput on the Digibeta, and then use the analog outputs from Multibridge for monitoring.
When working with a Betacam SP, connect the analog video and audio connections between the Betacam SP and the Multibridge SD. Then connect the SDI input and output of the DeckLink Plus to the Multibridge SD.
These two workflows will enable you to capture and record to Digibeta and also capture and record to Betacam SP.
Clearly you wish to switch between using the Betacam SP and the Digibeta. If you already have an SDI router, then use the video router to switch between these two workflows. If you don’t have a video router, then an inexpensive US$30 patch bay will enable you to switch between these two workflows. We also make the $4995 Workgroup Videohub which is an SD and HD SDI video router but it might be overkill for your needs unless you are also connecting to other workstations and decks.
Regards,
Luke Maslen
Blackmagic Design