There are many kinds of switches in electrical and electronic system. However, according to the number of poles and throwing method of the switch, switches can be classified into single pole and single throw switch, single pole and double throw switch, double pole and single throw switch, double pole and double throw switch. The difference can be show as the below:
1. single pole and single throw switch: it connects or disconnects one circuit with two positions, which is OFF and ON. The single pole and single throw switch has the most simple design.
2. single pole and double throw switch: it has one way for input and two way for output, which can connect to one of two circuits. Take a manual changeover switch as an example, It has three positions: Neutral, Primary and Backup.
3. double pole and single throw switch: it can control two separate circuits by one switch, turning to ON or OFF simultaneously. It could be found on load breaker switch LBS or disconnect switch.
4. double pole and double throw switch: two way for input and two way for output. It is basically two single pole and double throw switches used together. It could be found on automatic transformer switch ATS in electrical system.
