Exhibit 21 SUBSIDIARIES The following is a list of the subsidiaries of the Company as of October 19, 2001: Subsidiary State of Incorporation ---------- ---------------------- Telecommunications Transmission Business Segment CASI - Comtech Antenna Systems, Inc. Delaware CEFD - Comtech EF Data Corp. Delaware CSI - Comtech Systems, Inc. Delaware RF Microwave Amplifier Business Segment CPST - Comtech PST Corp. New York Mobile Data Communications Services Business Segment CMDC - Comtech Mobile Datacom Corp. Delaware 1