How to choose an industrial telephone？

How to choose an industrial telephone?
The selection of industrial phones is quite different from the selection of ordinary mobile phones. Generally, we choose mobile phones, and more focus on the appearance and performance of mobile phones. Industrial phones pay more attention to the practicality of the phone, the quality of the call, and the security.
Select the outer casing of the industrial phone

Due to the complexity of the industrial work environment, we generally use a metal casing, and the casing will be coated with anti-corrosion materials to achieve anti-destruction and anti-corrosion properties.The color of the shell will choose a striking color, red or yellow.
Industrial telephone requirements for communication technology

We can use analog or ip industrial phones. In the industry, we require normal communication at high and low temperatures, and the appearance is explosion-proof and flame retardant.
Telephone system selected by the entire industrial telephone

Now, the more mature technology is the ip pbx system. In the whole industry communication, we can use the ip pbx telephone system as the whole industrial telephone integrated system, and the ip pbx server cooperates with the dispatching station to control and dispatch the entire industrial telephone.
What else needs to be added?