So, if I want to use more relays what exactly do I have to buy?Work2Play said:as whlatimer said, a relay is basically an electronic switch. You supply power and it switches a set of terminals. In the case of the Piezo's you need a way to programmatically switch power on and off so the one built in Form C contact for Output 3 will do that. The "interior siren" wiring positions are for speakers so they can speak the voices - so the piezo's have to be handled on your own via rules.
Other uses for relays - garage doors (as mentioned above), strobes, buzzers (good for garage as warning), sprinklers, halloween decorations, etc.
Is it the ELK-M1XOVR 8voltage/8relay output expander?