From the Manufacturer
The fm136 wireless intercom/keypad is a versatile intercom system that allows for clear communication between a driver requesting entrance to the property, and a resident inside the property. The fm136 allows the user to communicate with the driver, grant or deny access, and open the gate from within the house. The system is ideal for any residential application, and it alerts you to the identity of visitors from the safety of your home. The intercom provides superior range with crystal clear two-way communication up to 500-Feet wireless, or up to 1,000-Feet direct wired. Comes with outdoor call/keypad unit that can be programmed with up to 25 entry codes for keypad access. The fm136 also comes with an indoor base unit that is mobile and can be used anywhere in your home just like a cordless phone. Rechargeable batteries allow for operation even during power outages. Multiple base units available separately for use within the home (maximum of 4).