Leviton 70A00-2 Cellular Communication Center (C3) Only products shipped and sold by Amazon.com (not third-party sellers) are eligible for full warranty and technical support offered by Leviton Provides backup phone service when lines are down or can be used as primary where landlines are not present Works with most standard security panels (and all Leviton home control systems) Uses mini-SIM card (25 mm  15 mm) Keep your home safe - even if a burglar cuts your phone line, your alarm panel can still communicate to the emergency personnel