This kind of control equipment mostly appears in the fire fighting lines. The common way is two-way power supply. One way is normal line power supply, the other way may be standby power supply from another transformer, or it may be power supply from diesel generator. When the power of external network is cut off, the standby power supply can be quickly started to ensure that the fire fighting is always in operation, When a fire accident occurs, it can be started in time, so how to install the dual power line, there are two options, one is the contactor controlled dual power switch, this switch is low cost, only suitable for ordinary equipment.

還有一種是雙電源轉換開關，它是供電氣設備使用的雙電源切換開關；接觸器組成的雙電源開關，用電時合上兩個空開斷路器，KM1得電吸合，甲常用電源閉合得電向負載供電，由于KM1吸合，乙電源的KM1常閉觸點彈開關閉電源。如果甲電源停止供電，那么乙電源的KM1處常閉點接通電源，時間繼電器工作使常開觸點閉合，使KM2得電吸合并自鎖，乙電源向負載供電，乙電源正常供電。

There is also a dual power switch, which is used for electrical equipment dual power switch; The double power switch composed of contactors, when using electricity, closes two air switch circuit breakers, KM1 is powered on and closed, and the common power supply of Party A is closed to supply power to the load. Because KM1 is closed, the normally closed contact of Party B's KM1 is opened and closed. If the power supply of Party A stops, the normally closed point of KM1 of Party B is connected to the power supply, and the time relay works to close the normally open contact, so that km2 is powered on and self locked, Party B supplies power to the load, and Party B supplies power normally.

雙電源轉換開關，它是原理是：可以在常用電源和備用電源之間進行自動轉換的開關。它是由一個或多個轉換開關電器和其他必要的電器組成，用來檢測電路，并且當常用電源出現故障時，通過雙電源自動轉換開關，自動將負載轉換到備用電源上，使用電設備能正常運行。

Dual power transfer switch, its principle is: can be in common power supply and standby power supply between automatic transfer switch. It is composed of one or more transfer switch electrical appliances and other necessary electrical appliances, used to detect the circuit, and when the common power failure, through the dual power automatic transfer switch, automatically transfer the load to the standby power supply, the use of electrical equipment can operate normally.

是一種安全可靠、自動化的、使用范圍越來越廣泛的電氣這種雙電源切換開關接線簡單，深受消防控制設備安裝人員的喜愛。在消防方面得到了良好的應用，使用也越來越廣泛，比如監控設施。

It is a safe, reliable, automatic, more and more widely used electrical equipment. This dual power switch has simple wiring and is deeply loved by the fire control equipment installation personnel. It has been widely used in fire protection, such as monitoring facilities.