What layer in the Transmission Control Protocol/Internet Protocol (TCP/IP) model is responsible for defining a way to interpret signals so network devices can communicate?

The data-link layer

Explanation:

The physical layer and data-link layer are often confused a lot especially in terms of what they do in the TCP/IP 7 layer protocol. The physical layer as the name suggests represents the physical devices like the cables and the connectors that join or interconnect computers together. This layer is also responsible for sending the signals over to other connections of a network. The data-link, on the other hand, translates and interprets these sent binary signals so that network devices can communicate. This layer is responsible in adding mac addresses to data packets and encapsulating these packets into frames before being placed on the media for transmission. Since it resides in between the network layer and the physical layer, it connects the upper layers of the TCP/IP model to the physical layer.