What is the difference between so-called front-mounted and back-mounted instruments?

In automation projects that use conventional instruments (with secondary instruments also being conventional), some of these instruments are installed on the dashboard surface, such as regulators, indicator instruments, recorders, operators, flash alarms, etc. These instruments are visible (through digital displays, pointers, color strips, etc.). Some of them require frequent operation (such as adjusting various parameters in regulators to match set values, operating the operator, changing paper in recorders, etc.)； Some instruments are installed behind the dashboard; they do not need to be monitored or operated frequently (such as indoor temperature transmitters, safety barriers, square roots calculators, adders, multipliers, signal distributors, power supplies, etc.). Control systems that utilize computer and network technologies such as DCS enable all functions such as indication, recording, regulation, and alarm monitoring to be carried out on the LCD screen of the DCS system; these functions are similar to those on a control panel. All calculations and signal processing take place within the DCS system, and may not be visible on the LCD screen; such functions are similar to those that occur behind the panel.