Lucent Technologies PARTNER Advanced Communications System Programming And Use Instructions page 275

If a system phone joins a call on a standard phone, there is a momentary
n
"break" in the call on the standard phone.
How to Join a Call
System Phone
A steady red light next to a line button indicates a call is in progress at another
extension.
To join a call:
n
n
Standard Phone
1. Lift the handset.
You hear intercom dial tone.
6 8
2. Dial
5-160
Feature Reference
Press the line button next to the steady red light and lift the handset,
or
Lift the handset and press
The red and green lights alternately flash. You are now joined with
the call.
and the number of the line on which the call is being conducted.
i
6 8 and the two-digit line number.