User guide

Key Extensions 63
Forum Phone 515 / 525 / 535: Extensions and Accessories
The power supply unit is plugged into the last in the series of key
extensions.
A system telephone requires a power supply unit if a key exten-
sion is installed. When using PoE, an IP system telephone requires
no power supply unit.
Connecting the Key Extension
CAUTION! Guard against static charges!
Static charges can damage the Forum 523/524’s electronic
components. Make sure you discharge yourself and your
tools before and during any installation work on the
Forum 523/524 and any connected terminals. Use dis-
charging underlays or antistatic mats where possible.
Please note: Never attach a key extension to a system tele-
phone that is already connected to Forum 523/524. Pull the net-
work cable out of the socket before screwing the key extension
onto it.
Configuration Needs Power Supply
Unit
U
pn
system telephone No
U
pn
system telephone with 1-3 key
extensions
Yes
IP system telephone Yes
IP system telephone with 1-3 key
extensions
Yes
IP system telephone with PoE (Power
over Ethernet)
No
IP system telephone with 1-3 key
extensions and PoE
No