ZyXEL Communications ISG50-ISDN Application Note page 8

You can either add SIP peers one by one or add multiple SIP peers at a
time.
Here, we add multiple SIP peers.
Define the start number and the amount of extensions.
Here, we set 3100 as the start number.
The passwords for these SIP peers are the same as the extension
numbers. In order to make the password more secure, we add a
prefix number to these extensions.
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