Name for one of the two wires in a telephone twisted pair, according to USOC. (Compare to ring.)
Typically the reference voltage line on copper telephone communications pairs from standard voice telephone circuits up to DS-3 lines. The term is sometimes used in digital communications cables (e.g. Ethernet) to determine the transmit line.
Historically, tip was the "tip" of a plug which resembled a 1/4" stereo connector.
The tip in residential telephone wiring is the green, black, or white wire for lines one through three, respectively. For high-density wiring as run by telephone companies, the tip is usually has a white jacket with a colored stripe. In RJ modular connectors like RJ-45 and RJ-11, tip lines are the odd-numbered pins.
It should be noted that most standard contemporary telephones are not subject to restrictions on polarity of the telephone circuit. Tip and ring may be reversed (usually accidentally) in household wiring with no effect on telephone sets.