In this paper a modification of the DCSK (Direct chaos shift keying) is considered. This modification, instead of using the reference signal part as in DCSK, transmits the information bit without it. The receiver then uses a unique key, known only to it and the sender, to decode the bit. The effectiveness of the system and two ways of its realization are tried, with this paper describing the experiments that are held. The effectiveness is defined by systems capability to transmit data. The theoretical experiments include testing five different keys and testing noise resistibility. The practical experiments include production of two models of the system, their comparison in functional and synthesis levels. The experiments are successful if the system model can be implemented in both ways that are tried, it is implemented in both ways, and the synthesis results are comparable.