Referring to the Physical Layer of the OSI Reference Model. See also OSI Reference Model and Physical Layer.
"Layer 1." YourDictionary, n.d. Web. 14 August 2018. <http://www.yourdictionary.com/layer-1>.
Layer 1. (n.d.). Retrieved August 14th, 2018, from http://www.yourdictionary.com/layer-1
See OSI model and physical layer switch.