best free conference call service

{"title":"102 Inch Interactive Whiteboard Projector Screen Board For School Conference","imgUrl":"https:\/\/img.silkroadsl.com\/nimg\/65\/0a\/a94943f78ef354a097db1a1c80a6-200x200-1.jpg","attrs":{"Brand Name":"iBoard or OEM","Minimum Order Quantity":"10","Delivery Time":"30 days","Surface":"Nano or Ceramic (Optional)","Installation":"Wall mounted, cabinets, mobile stand (optional)","Color":"Silver, Grey, Black, Grey (Other colors optional )","Application":"Education, School, Business, Presentation...","Certification":"CCC, CE, FCC, RoHS, Reach, OHSAS, ISO9001, ISO14001","Size":"102\" 82\/86\/90\/96\/120inch available","Ratio":"16:9\/ 16:10\/ 4:3","Warranty":"1 year","Place of Origin":"Shenzhen, CHINA","Packaging Details":"Carton Package","Payment Terms":"T\/T, L\/C","Supply Ability":"10000 units per month","Aspect Radio":"16:10, 16:9...","Interface":"USB, VGA, RS232, HDMI","Screen Size":"65\",75\",86\", 98\"","Multi-Touch":"Up to 40 points","Hotkeys":"Two sides hotkeys","Shipping Way":"Sea Shipping Air Freight Truck Freight","Touch Points":"20 points","Power Supply":"AC 100-240V, 50\/60Hz","Operation System":"Andriod\/Windows\/Linux\/Mac.etc.","Accuracy":"2mm","Mobile Stand":"Optional","Colors":"Black Or OEM"}}