Exhibit 21 SUBSIDIARIES The following is a list of the subsidiaries of the Company as of October 22, 1999: Subsidiary State of Incorporation - ---------- ---------------------- Telecommunications Transmission Business Segment CASI - Comtech Antenna Systems, Inc. Delaware CCC - Comtech Communications 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