The node detector is a receptor. It changes its state when either any node or a specific node is detected. Right-click it to set a nodename to scan for. It can also receive digiline signals. You can either send "GET" and it will respond with the detected nodename or you can send any other string and it will set this string as the node to scan for. Nodenames must include the mod they reside in, so for instance default:dirt, not just dirt.