A:Answer Hello Jason, thank you for reaching out to us with your question. In a three-way configuration, it will require a primary (45857GE) and our add on switch (12723) https://www.bestbuy.com/site/ge-smart-lighting-control-in-wall-add-on-switch-white/2622015.p?skuId=2622015. Yes, the primary switch can be used by itself without incorporating the old non-smart switch. However, if you prefer to use both switches, the add on switch is necessary. The smart switch is Alexa compatible, however, it requires a ZigBee certified gateway hub such as; Wink, Samsung’s Smart Things Hub and Logitech Harmony Home Hub Extender. If you have any further questions, please don’t hesitate to respond or give us a call between the hours of 7:00 AM – 8:00 PM Central Standard Time, Monday thru Friday at 1-800-654-8483. Thank you.