EXHIBIT 21 SUBSIDIARIES OF INTERDIGITAL Company Jurisdiction / State of Incorporation ------- ------------------------------------- Digital Cellular Corporation Pennsylvania InterDigital Asia KK Japan InterDigital Canada, Ltee. Delaware InterDigital Finance Corporation Delaware InterDigital Mobilecom, Inc. New York InterDigital Technology Corporation Delaware InterDigital SE Asia, Ltd. Pennsylvania InterDigital Telecom, Inc. New York Universal Service Telephone Corp. Nevada USTC Supply Corporation Nevada USTC World Trade Corporation Nevada Wireless Digital Networks, Inc. Pennsylvania