Abstract: To overcome the shortcomings of traditional equipment of frequency-shifting automatic block, a three-display frequency-shifting automatic block transmitting device was designed. It uses a single-chip microcomputer as the main componen,t an external timer/counter and some simple auxiliary circuits to produce frequency-shifting and low frequency modulation signals. This design provides the equipmentwith high reliability and flexibility. It can also adapt itself to the transmitting equipmentwith 4-, 8-even 18-displayswith a slight extension ofhardware and simplemodification of software.