There are two wired modes: 485 transmission mode and M-BUS transmission mode. The main characteristics of 485 transmission mode are four lines (two power lines and two signal lines), which need to distinguish the polarity of the line; The main feature of M-BUS transmission mode is that two lines are used as power supply and loaded with signals, and the two lines do not distinguish polarity.
Wired meter reading can be divided into pulse type (active), camera type (passive), resistance type (passive) and photoelectric type (passive) according to different technical implementation methods. In terms of technical reliability, development direction and market share, photoelectric mode is the mainstream mode.
The meaning of direct reading meter is that it does not supply power at ordinary times, and it supplies power for meter reading.