Can I use an ES-105A v3 as a Power over Ethernet Switch

Hi @keith21250 ,

Welcome to Zyxel Community!

ES-105Av3 is not a PoE Switch, so it doesn't have PoE feature.
Here are some other PoE model for you to reference:

• PoE12-HP  - It is a PoE Injector for the user that only needs one PoE port.
  https://www.zyxel.com/products_services/802-3af-at-PoE-Injector-PoE12-HP/
• GS1005HP - It is an Unmanaged Switch with 4 PoE ports.
  https://www.zyxel.com/products_services/5-Port-GbE-Unmanaged-PoE-Switch-GS1005HP/
  
• GS1200-5HP - It is a Web Managed Switch with 4 PoE ports.
  https://www.zyxel.com/products_services/5-Port-8-Port-Web-Managed-PoE-Gigabit-Switch-GS1200-5HP-v2-GS1200-8HP-v2/
  
• GS1350-6HP - It is a Smart Managed Switch for Surveillance with 5 PoE ports.
  https://www.zyxel.com/products_services/Smart-Managed-Switch-For-Surveillance-GS1350-Series/
  

Hope it helps.