911 Call Blocker - Restrict Outgoing calls - Specify Allow & Disallow Outbound Phone Numbers, Area codes, Prefixes It works on any standard analog phone lines (PSTN and VOIP) FSK or DTMF compatible Programming is done locally or remotely via the dialpad of any DTM telephone Line powered (no batteries required) - Size: 4" x 2.5" x 0.9" - Weight: 3 ounces It can be programmed to block dialing of any specific outgoing phone number, area code, or prefix. Disclaimer: In some states there are laws stating that you cannot block access to 911 calls. It's your responsibility to make sure you are not in violation of these laws.