FIELD: modulating digital communication systems; modulators, demodulators, and control devices using infrared radiation. SUBSTANCE: zero bit is inserted in digital data stream prior to coding in NRZI format each time when five sequential on- bits are detected in stream. Flashing pulses are shaped each time values of data reduced to NRZI format change. Demodulator changes value of received signal when receiving flashing pulse with the result that output signal is shaped in NRZI format. This makes it possible to use automatic phase control ring of controller for synchronous data transmission and reception; in this case, receiver may be phased out with received data, and DC component of received signal is effectively eliminated. EFFECT: provision for maintaining synchronous and asynchronous modes of operation. 15 cl, 3 dwg
