Procedure

GPIO outputs on Q-SYS core processors are often used to control projector screens, window shades, etc., via external relays. If core processors are set up as a redundant pair, you can use a relay to select the GPIO of the one that is active.

When configuring the GPIO outputs, select Open Collector. Add a 12-volt DPDT relay, such as a common automotive accessory type, and connect it as shown in the diagram. When the primary core processor is active, it energizes the coil of the relay and the normally open (NO) contacts passes the control lines from the primary core processor to the UP and DOWN relays. If the primary core fails, the relay coil de-energizes and the normally closed (NC) contacts switch over to the control lines from the backup core processor.