To avoid electric shock, do not connect safety extra low voltage (SELV) circuits
to telephone network voltage (TNV) circuits. LAN ports contain SELV circuits,
and WAN ports contain TNV circuits. Some LAN and WAN ports use RJ-45
connectors. Use caution when connecting cables.
The following warnings apply when you use the external power supply with the
Cisco IP Phone:
This product relies on the building's installation for short-circuit (over current)
protection. Ensure that a fuse or circuit breaker no larger than 120 VAC, 15A U.S.
(240 VAC, 10A international) is used on the phase conductors (all
The device is designed to work with TN power systems.
Cisco IP Phone 7960 and 7940 Series User Guide