Safe extension numbers

• Three or four digit extensions are recommended.  Five digit is OK.

• Avoid beginning an extension with "9...", unless you use a dial-out prefix other than "9".

• Avoid "90..." at all times.
  (call parking is 9000-9050)

• Avoid "91..." in the U.S.

• Avoid 85, 86, 87, 88, 89 as the beginning digits of any extension.
  (voicemail and conference bridges use 8500-8599, for example)

• Do not begin three digit extensions with an "8" or "9".
  (Otherwise, you will experience dialing delays as the phone waits for you to enter more digits)

• Extensions may not begin with a "0".

Recommendations:

1. We recommend starting extensions with a fairly high numbered digit, such as 6 or 7.  Lower numbered digits such as "1" are OK, but bear in mind that if you want to use keypress options on your AutoAnswer: edit call menu, extensions starting with "1" could pose a conflict with keypresses such as "For Acme Widgets, press 1".

2. We do not recommend mixing extension number lengths.
   (mixing 3- and 4-digit extensions can cause delays when dialing three-digit extensions, as the phone may wait for a fourth digit)