The DoorKing 1504-091 is a Stand-Alone Digital Keypad Access Control with Intercom, to flush mount. Connect the intercom substation to a master intercom station for voice communications. The 1504-081 is flush mount keypad that can store up to 400 PIN codes. The codes consist of 4 or 5 digits. This is a sturdy unit with a lighted metal keypad, stainless steel faceplate and weather-resistant steel cabinet. You can program PIN (personal identification number) codes from the keypad or a DoorKing smartphone app. The EEPROM memory won't lose programmed codes during power outages. Control access to your gated community, apartment complex, parking facility, commercial building or self-storage facility.