Scope:This document will help you determine which VOIP phone is ideal for your needs. Both Door Entry phones do allow to be connected to a Door Strike, Mag Lock, Gate Controller, etc via COMMON and NORMALLY OPEN contact to operate the strike.Requirements:Door Strike, Mag Lock, Gate Controller (Optional)Door Entry Phone with No Keypad (VIKING E-20-IP VOIP ENTRY PHONE)You will want to use this device if the client wishes the visitor to click a button to call a group of extensions. This also means their employees have another way to enter the door without calling in using the device (such as a Key, Key Card, or Fob) Door Entry Phone with Keypad (VIKING K-1700-IP VOIP ENTRY PHONE)You will want to use this device if the client wishes the visitor to click a button to call a group of extensions and also allow their employees to buzz in themselves without a key.