用SCI语言对这句话润色：This design completes a 4G-based in-car intercom system. The system design is built using modules such as s

This paper presents the design of a 4G-based in-car intercom system, which comprises signal transmission, signal processing, and 4G public network modules. A dual-mode intercom system based on 4G communication technology is proposed for in-vehicle communication. The paper analyzes the market demand for 4G intercom systems and introduces the overall system, flowchart, function design, and circuit analysis of each module based on the classification of intercoms and their working principle. The system includes a transmitter, receiver, modem circuit, central controller, and 4G base station with straight-through mode and public network trunking mode. The initial system operates in straight-through mode, but when the communication user is far away or the environment is harsh, the public network trunking intercom system can be used. Compared to traditional intercom systems, this system exhibits higher interference immunity, high spectrum utilization, superior call quality, easy signal encryption, and longer transmission distances.