AMIKON Industrial Automation YOKOGAWA SB301 Part Number SB301 Application & Failure Scenarios The SB301 is used for ESB bus communication between a field control unit and connected node units in the applicable Yokogawa control-system configuration. It may be investigated when ESB communication is interrupted or an interface-card fault is suspected. In a dual-redundant arrangement, the active and standby SB301 cards are managed by the active CPU. If an abnormality is detected