Comparison between digital intercom and analog intercom

    Traditional  analog  intercom  use analog signals to transmit messages, which have disadvantages such as low frequency utilization, severe mutual interference, single business functions, unstable communication, and difficult management and control. Digital Intercom are a communication method that digitizes analog signals through digital encoding and modulation, and optimizes them using digital signal processing methods.

    In digital intercom, analog voice signals are first converted into digital signals through A/D conversion and speech encoding. Due to the narrow bandwidth of digital intercom, usually 12.5kHz or 6.25kHz (analog 12.5kHz or 25kHz), the speech encoding in digital intercom generally adopts parametric encoding method, which does not encode the waveform of the speech signal, but extracts the feature parameters that generate the speech signal and encodes them for transmission. The transmission rate is generally between 1.2-4.8kb/s, which can meet the bandwidth requirements of digital intercom.

    The main purpose of channel encoding and decoding is to improve the reliability of digital transmission systems. By adding some redundant symbols as supervision codes for error control in the output sequence of speech coding according to certain rules, the receiver can detect errors or automatically correct them based on these rules to achieve this.

    Analog Intercom generally use methods such as frequency inversion for information encryption, which is simple and easy to crack. Digital intercom use digital encryption to protect users' information, which is more competitive in some special industries such as civil aviation and railways that require high information security. There are many methods of encryption, such as performing modulo-2 encryption on a digital signal and a long period of m-sequence to complete encryption. The receiving end uses the same m-sequence and the received encrypted signal to perform modulo-2 encryption again, completing decryption.

    Compared with analog intercom, digital intercom have strong anti-interference ability, good call quality, high frequency utilization, good confidentiality performance, support for data services, facilitate error free relay, and facilitate the use of a set of digital relay systems, which conforms to the laws of communication development. Undoubtedly, digital intercom are the direction of walkie talkie technology development and will gradually replace analog intercom.

    In today's building intercom market, although TCP/IP fully digital building intercom technology and functions have far surpassed traditional analog intercoms, the "timeline" left and right by the market is only moving at an approximate turtle speed, so traditional intercom products are still favored in the market, because there is a great distance between digital visual intercom and the times.