We use these in Kiosks for Truck Scales at Grain Elevators. Also installed many at Assisted Living Facilities.The programmable button can ring up to two phones (through Asterisk PBX can do about anything). We have built many, many, many custom Asterisk systems and use these door phones frequently. The item "SIP VoIP IP Weather Proof Door Phone withRelay Asterisk, Polycom, Other VOIP PBX" is in sale since Tuesday, October 1, 2019. This item is in the category "Business & Industrial\Office\Telecom Systems\Business Phone Sets & Handsets". The seller is "tek4ufast" and is located in Mayville, Michigan. This item can be shipped to United States.