What is a Duplex Communication System?

Duplex communication means that information can be transmitted in both directions at the same time. Just like making a phone call, you can also listen while speaking, and listen while you speak. This duplexer, which is capable of working simultaneously on two different frequencies (there are certain requirements for the difference between the two frequencies), is also called a duplex duplexer.

Duplex communication

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Duplex communication means that information can be transmitted in both directions at the same time. Just like making a phone call, you can also listen while speaking, and listen while you speak. This duplexer, which is capable of working simultaneously on two different frequencies (there are certain requirements for the difference between the two frequencies), is also called a duplex duplexer.

Duplex communication

Duplex machines include duplex handsets, duplex in-vehicle machines, and duplex bases / transmitters. Duplex handsets mostly work across segments in the VHF and UHF bands. Duplex handsets are generally referred to as cross-segment duplex handsets. When it works, it can transmit by VHF or UHF, or transmit by UHF or VHF. However, this problem does not exist for duplex vehicle-mounted machines and bases / transmitters. It can work across segments and can also be made into the same frequency duplex (VHF or UHF band). Due to the use of a duplexer that separates the transmit and receive signals or the use of a dual antenna that separates the transmit and receive, as long as there is a certain frequency difference in the VHF and UHF bands (the national standard VHF band is 5 ~ 7MHZ, the UHF band is 10MHZ) can complete the same frequency duplex work. Although the duplexer is easy to use, the circuit design is more complicated and the price is higher, especially in the use of frequency resources is extremely uneconomical, so in addition to special occasions need to use the duplexer (handset and base / repeater) In addition, duplex in-vehicle machines have rarely been used in domestic professional communications (in the 1980s, in some industries, such as water conservancy, power system UP450, KG106 and other imported models and domestic duplex band machines. By the 1990s Most of them are no longer used). Duplex machines are used on special occasions, that is, the relay station for forwarding or the base station for command. Another feature of the duplexer is that, as a duplex base station, the wireless network and the wired network can be connected through the interface device. This interface device has a wireless connector (also called an adapter). Through it, the wired telephone can talk to the wireless intercom, otherwise the intercom can make a wired telephone by dialing. This kind of equipment was very popular in China from the late 1980s to the middle and early 90s. At this point, simplex machines are impossible. Because the receiving and sending of simplex machines are the same frequency. In the full-duplex trunking communication system in the mid-1990s, the cross-section trunking duplex hand-held walkie-talkie and on-vehicle unit, which are known as "small big brothers", had a short history. The transmission frequency of its base station is UHF, and the reception frequency is VHF. Conversely, the transmission frequency of the mobile station is VHF, and the reception frequency is UHF. These cross-section duplex handheld walkie-talkies include IC-W21AT, IC-T21CP / T31CP from Japan ICOM, TH-78A / 79A from Kenwood Japan, AT68C / 88C, X98C from Taiwan Analog Devices, and TH82 from Shenzhen Tianlitong . Cross-segment full-duplex vehicle-mounted stations include IC-281H / 481H from Japan ICOM, TK-733 from Japan Kenwood, TH811 from Shenzhen Tianlitong, and MR588 from Taiwan ADI. In the late 1990s, with the popularization of "big brother", the price was reduced, the volume was reduced, the use was convenient, and the functions were increased. The cross-segment duplex communication system quickly changed from "shared network" to "dedicated network" All have been eliminated, and only a few dedicated cross-segment duplex communication systems are in operation.