Wide and narrow band intercom，Bringing together broadband and narrowband technologies，Beifeng TP800 public integrated walkie-talkie (wide and narrow integrated walkie-talkie) is a DMR professional intercom and public network intercom functions combined into an intelligent public integrated walkie-talkie，Support public network mode, private network mode, mixed mode, relay mode four modes free switching, its dual-mode intercom, public independent PTT, cross-network relay and rich customization functions (positioning, recording, Bluetooth, intelligent management platform, etc.)。

　　Basic principle

　　1. Frequency range:

　　Narrowband communication: Traditional radio frequencies are used, and the spectrum width is narrow, which is suitable for voice communication and some low-speed data transmission。

　　Broadband communication: The use of a wider spectrum, can support higher data transmission rates, suitable for video, high-speed data, etc。

　　2, signal processing:

　　Digital signal processing: The fusion walkie-talkie processes signals through the digital signal processor (DSP) to achieve the encoding, modulation, demodulation and decoding of voice and data signals。

　　Adaptive modulation: Automatically select the most suitable modulation mode according to the communication environment to maintain the stability and efficiency of communication。

　　Work flow

　　1. Launching process:

　　When the user speaks, the microphone converts sound into electrical signals。

　　The signal is digitized by DSP and encoded and modulated in narrow band or wide band mode according to communication needs。

　　The modulated signal is amplified by a power amplifier and then transmitted by an antenna。

　　2. Transmission process:

　　The broadband signal is transmitted through the antenna like narrowband, but because of its wide bandwidth and high data transmission rate, it has higher requirements for signal strength and transmission environment。

　　In the transmission process, some advanced modulation techniques (such as orthogonal frequency division multiplexing - OFDM) may be used to improve spectrum utilization and anti-interference ability。

　　l The transmission distance of broadband signals is shorter than that of narrowband signals, and the signal attenuation may be more pronounced when encountering obstacles。Therefore, in actual use, broadband communication is more applied to scenarios with short distance and high quality communication requirements。

　　3. Receiving process:

　　After receiving the signal, the antenna first passes through the low noise amplifier (LNA) for initial amplification。

　　l The amplified signal is sent to DSP for demodulation and decoding。In this process, the demodulation process will be more complicated due to the large amount of data in the wideband signal。

　　The decoded digital signal is converted into an analog signal, and the sound is played out through the speaker。