# Set RCOS System-Wide Parameters

To enter the starting and ending NPA (area code) and NXX (three-digit prefix) digit positions:

1. Complete an RCOS worksheet.

2. - From the Main Menu, select (S) System Maintenance, (R) Reconfiguration, (M) Restriction COS, and then (D) Define System Wide Parameters.
3. - Count an example dial string your server can use to locate the starting and ending digit positions for the NPA (area code) and the NXX (three-digit prefix). For example, the settings for a North American ten-digit phone number are:

   - The starting NPA digit position is 10

   - The ending NPA digit position is 8

   - The starting NXX digit position is 7

   - The ending NXX digit position is 5

4. Select (A) Starting Digit Position of NPA and enter the n umber of the digit position at the start of the NPA.

5. Select (B) Ending Digit Position of NPA and enter the n umber of the digit position at the end of the NPA.

6. Select (C) Starting Digit Position of NXX and enter the n umber of the digit position at the start of the NXX.

7. Select (D) Ending Digit Position of NXX and enter the n umber of the digit position at the end of the NXX.

8. Exit the RCOS menu to save your settings.