You can connect the analog buses of multiple adjacent NI SwitchBlock carriers with the NI 2806 expansion bridge for the NI SwitchBlock.
Note   If you connect multiple carriers with the expansion bridge, you cannot connect to the analog bus on any of the connected carriers until the drivers for all connected carriers have been loaded by the system. This prevents unintentional shorts between channels across the analog bus. You may still manipulate relays directly using the niSwitch Relay Control VI or the niSwitch_RelayControl function, but with the risk of shorts across the analog bus.

The following figure shows where to insert the NI 2806 expansion bridge.



1 NI PXI/PXI Express Chassis
2 NI PXI-2800 Carriers
3 NI 2806 Expansion Bridge
If the analog buses of multiple adjacent carriers have been connected, you can enable devices in both carriers to connect to the same analog bus line simultaneously using the Analog Bus Sharing Enable property or the NISWITCH_ATTR_ANALOG_BUS_SHARING_ENABLE attribute.
Note   NI recommends using NI Switch Executive to operate systems that contain multiple carriers. The NI Switch Executive Help includes information about using NI Switch Executive to create virtual devices that span multiple carriers.