| Popis: |
Abide by the design principles of mine intrinsically safe circuit, according to the need of underground communication in coal mine, the paper proposed a design scheme of DC carrier telephone which can dial. The design circuit of the telephone is introduced in detail. The telephone’s voice signals are generated by the microphone. After enlarged then the voice signals are modulated to frequency signals by LM567 chip. The frequency signals are coupled by transformer and then transmitted by 12V DC power supply line to the other voice terminals. In the voice terminal the signals are demodulated by LM567 demodulation circuit and enlarged by LM386, then, the amplified audio signals are output from a speaker. The dialing circuit is designed based on the STM32 MCU. The dial information is transmitted to the other telephone terminals by CAN bus. The measured distance calls is greater than 2000m, volume is larger than 85dB, good results. |
