REXCOM <RXSC> TO ACQUIRE MARKETING FIRM Rexcom Systems Corp said it agreed to buy all the assets of Postech Inc from Comtech Group International Ltd, a Canadian computer service company, for 70 pct of Rexcom's voting shares. The purchase will be for Rexcom common and preferred stock. Postech, the Canadian firm's U.S. marketing arm, sells computerized restaurant management systems and security systems in the U.S. The deal is subject to approval by the boards of Postech and Rexcom.