What You'll Need To Do Programming; Using Buttons - Northern Telecom Compact ICS 4.0 Manual

What you'll need to do programming

Programming is done using a telephone that can show two lines
of information on its display. Examples of telephones with two-
line displays are shown on page 3.
You need a programming overlay to show which buttons to press
when you are doing programming. See ''The programming
overlay'' on page 6.
When you use a telephone for programming, it is taken out of
service. This means it is unable to receive or make calls, and the
call forward features do not work. Do not use the main reception
telephone for programming because you may lose incoming
calls.

Using Buttons

The two-line telephone you use for everyday calling is used for
changes and maintenance. Examples of telephones with two-line
displays are shown in the illustration.
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Getting started with Norstar / 3
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Compact ICS 4.0 System Coordinator Guide