e4d47c27__DataSheet_for_product_XE2422H__description
[pin] 2 [name] ring [description] 
The Ring and Tip signals connect the modem to the telephone line. FCC Part 68 Rules require a 1500 volt isolation barrier between the telephone line and all other circuits. This isolation must be preserved throughout the system. The telephone company places a DC “ Battery” voltage across Tip and Ring on public switched telephone lines. The XE2422H operates regardless of the polarity of this voltage. The “ Battery” voltage drives up to 120 milliampere of DC loop current. UL60950 requires minimum creepage and clearances distances between the Tip and Ring traces and all other circuits. Clearance is the shortest distance between conductive circuits; creepage is the distance between conductive points along the surface.
Cermetek DataSheet for product XE2422H
description