A transfer switch is a low-voltage switch that can switch multiple circuits. The main types include single-pole transfer switches, double-pole transfer switches, three-pole transfer switches, four-pole transfer switches, and double-pole double-throw transfer switches. There is also a special multi-functional transfer switch.

The single-pole transfer switch (SPST switch) is a simple type with only one set of switch contacts, used to control the on-off of a single circuit. The double-pole transfer switch (SPDT switch) has two different sets of contacts and can simultaneously control the on-off of a circuit, commonly used in speaker selectors, audio systems, etc. The three-pole transfer switch (SP3T switch) has three contacts and can control three different circuits, commonly used in Wi-Fi routers. The four-pole transfer switch (SP4T switch) has four contacts and is used to control four circuits, commonly found in the communication field. The double-pole double-throw transfer switch (DPDT switch) has two sets of on-off contacts and can simultaneously control two different circuits, widely used in household appliances and for controlling devices such as light bulbs and motors. 

The multi-functional conversion switch is a more powerful type of switch, consisting of multiple contacts, an operating handle, and some auxiliary devices. It has a compact structure, is easy to operate, and offers flexible control. It can switch, control, and protect the circuit according to different working conditions. Multi-functional conversion switches are classified as single-pole, double-pole, multi-pole, lock-equipped, and indicator-equipped types. By rotating or pushing the operating handle, the contacts can be switched, thereby controlling the circuit. 

The contact-type switch of the conversion switch mainly relies on mechanical actions to complete the conversion, while the static switch adopts a non-contact design, with shorter power switching time and is suitable for scenarios requiring uninterrupted power supply.