Users who use the public network walkie-talkie know that they must speak after pressing the PTT button and hear the "drop" sound. This is obviously different from the traditional analog or digital conventional walkie-talkie, and some users use the public network walkie-talkie when they first use the public network walkie-talkie. Not used to it. Why use the public network intercom, if you press the PTT button to start talking, the receiving end is prone to the phenomenon of the first few words (previously lost words)? This is because there is a time difference between the public network radio and the completion of the establishment of the intercom group by pressing the PTT button. This time difference is called "group call setup delay". Definition of several delay indicators related to public network intercom Regular intercom VS cluster intercom Traditional walkie-talkies are divided into "regular walkie-talkies" and "cluster walkie-talkies." Regular intercom Each intercom group needs to monopolize one radio channel (frequency point), and multiple intercom groups need to occupy multiple independent radio channels (frequency points). Cluster intercom By using the central base station control, wireless channel sharing can be realized. Each intercom group only occupies the wireless channel when the intercom call occurs, and the channel resources are released after the intercom is finished, and the same channel can be used by different intercom groups. It is precisely because the conventional walkie-talkie adopts the mechanism of exclusive channel. When the user presses the PTT button, the walkie-talkie starts to transmit signals, and there is no channel resource application and allocation process, so no need to speak the sound, and press the PTT button to speak. The cluster intercom system is different. For example, TETRA and iDEN use the shared channel mechanism. The number of user packets is much larger than the number of available physical channels. When a terminal initiates a group call, it needs to apply for channel resources to the base station first, and obtain the resources allocated by the base station. After confirming, it can occupy the wireless channel and start speaking. Therefore, the user who has used the cluster walkie-talkie knows that after pressing the PTT button, the voice confirmation tone will be heard before speaking. Public network cluster intercom The working principle of the public network intercom is similar to that of the digital trunking system. Therefore, it should be called “public network cluster system†or “public network cluster intercom system†more accurately. In fact, users on the public network intercom should not only share wireless channel resources with other public network intercom users, but also share wireless channel resources with mobile phone users. However, due to the large number of base stations on the mobile public network, large system capacity, and large coverage, there are many advantages compared with the private network digital trunking system. Especially in the 4G network with large bandwidth and low latency, its business functions, performance and system capacity are more obvious. The group call setup delay is one of the key indicators of the intercom service of the public network cluster, which has a great impact on the user's intuitive experience. The group call establishment delay index of the traditional Tetra digital trunking system is less than 300ms. The early public network intercom system based on 2G mobile network was due to the excessive delay of group call establishment, and it was unstable, sometimes it took several seconds to establish, resulting in poor user experience and poor market development. This indicator has been greatly improved under 3G and 4G network networks. RAM/RFM Intermediate Frequency Capacitors RAM/RFM intermediate frequency capacitors Intermediate Frequency Capacitors,Induction Heating Capacitors,Furnace Resonant Capacitor YANGZHOU POSITIONING TECH CO., LTD. , https://www.yzpst.com