They don't use any components except connectors.
Both boards are different:
- The MV-ELD 1/2 board has two connectors: one for the MV-ELA board, and another one for chaining the MV-ELD 2/2 board.
- The MV-ELD 2/2 board has only one connector.
The 3 or 6 panel version is the MV-ELC.