Modbus is a serial communication protocol developed by Modicon published by Modicon® in 1979 for use with its programmable logic controllers (PLCs). In simple terms, it is a method used for transmitting information over serial lines between electronic devices. The device requesting the information is called the Modbus Master and the devices supplying information are Modbus Slaves. In a standard Modbus network, there is one Master and up to 247 Slaves, each with a unique Slave Address from 1 to 247. The Master can also write information to the Slaves.

wireless 4g router with sim slot Modbus protocol is a universal language that used in electrical automation electronic controllers. This protocol allows controllers as well as other network devices to communicate with each other, and it became an industry-standard protocol. Modbus protocol has good interactivity and open standards and has been widely used in the industrial field.

Modbus has two communication modes: ASCII and RTU, Modbus-RTU(Modbus Remote Terminal Unit) and Modbus-ASCII(American Standard Code for Information Interchange). Although there are two communication modes, only one communication mode can be selected when using, and mixed-use is not supported.

Modbus is an open protocol, meaning that it's free for manufacturers to build into their equipment without having to pay royalties. It has become a standard communications protocol in industry, and is now the most commonly available means of connecting industrial electronic devices. It is used widely by many manufacturers throughout many industries.Modbus is typically used to transmit signals from instrumentation and control devices back to a main controller or data gathering system, for example a system that measures temperature and humidity and communicates the results to a computer. Modbus is often used to connect a supervisory computer with a remote terminal unit (RTU) in supervisory control and data acquisition (SCADA) systems. Versions of the Modbus protocol exist for serial lines (Modbus RTU and Modbus ASCII) and for Ethernet (Modbus TCP).