The following diagram follows the path of the Scanning Interface Unit (SIU) v2.2 relay enable and external enable circuit.

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Notes:

• Scanning Interface Rev 2.2 is printed on the card inside the SIU.
• SEII Rear Panel Connector is that of the computer card.
• Scanning I/O B is an SIU rear panel connector.
• The circuit shown is inside the SIU.
• The SEII generates a single logic signal which drives Q1.
• Q1 drives relay RL7.
• RL7 provides a 12V signal (RELAY_EN) to the rest of the relays on the SIU board.
  Schematics for these relays can be found with their respective circuits.
• The RELAY_EN signal also drives external enable relay RL4.
  This external enable signal routes to the microscope via Scanning I/O B pin 2.
• The external enable input (Scanning I/O B pin 1) comes in from the microscope,
  and can be either passed through or used as the external enable source signal.
• The three jumpers can be configured to handle a variety of interface situations. Contact support for more information.