An adjusting circuit of duty cycle includes an edge detecting circuit, a flip-flop connected to the edge detecting circuit, a feedback control circuit connected to the flip-flop and a charge pump circuit connected to the feedback control circuit. In the codeword to symbol relation, a plurality of sample symbols corresponds to a plurality of codewords. The light guide projection further includes an inclined surface on a side adjacent to a light source to prevent the light guide projections from cracking. The nature of the coating provides controlled release of the bioactive substance from the encapsulate.