Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems Can the 218 switch HDMI sources through the HD621

As you say that does work great.

The OP is asking about 218 and HD621 the 218 does not have BNC comms. The only "comms" available on the unit is on the SL connections.
You can tap into the comms bus on either the SL output master connection or on the SL input connection.