Tee connector Wikipedia
A Tee connector is an electrical connector that connects three cables together. It is usually in the shape of a capital T. It is usually used for coax cables and the three connector points can be either female or male gender, and could be different or the same standard, such as F type BNC or N type.
Tee connectors can be used to split radio frequency power from a cable into two. It could be used to attach a piece of electronic test equipment. T connectors were much used on co-axial 10M ethernet networks.