Mechanical relay switches are assigned a notation based on their function and other characteristics. Some examples are: GQ, GN, CM, CT, DQ, etc.

Types of relays based on the switch are:

§         SPST: Single pole, single throw. These have a single pole and only one position.

§         DPDT: Double throw, double poles. The number of poles and throw is two.

 

Applications:

They are used in industrial controls, telecommunications, automotive, home appliances, computer peripheral, security systems, etc.