Analysis of information sources in references of the Wikipedia article "Category 5 cable" in English language version.
carry one old fashioned analog telephone signal and one 10/100 Mbps Ethernet signal by the same single network cable.
Since 10base-T or 100base-TX wiring uses 2 pairs (4 wires) and each analog phone connection uses a single pair (2 wires) you can, subject to limitations, run 2 telephone connections and LAN traffic on category 5(e) wiring.