Introduction to Marine Engineering

Switches are devices that can open or close the circuit path, controlling the flow of current. They are used to turn devices on or off and control the circuit’s operation.

Switches are available in a wide variety of forms suitable for different applications.

Single-Pole, Single-Throw (SPST) Features a single input terminal and two output terminals, enabling a simple on-off switching action to connect or disconnect a circuit.

Single-Pole, Double-Throw (SPDT) With a single input terminal and two output terminals, this form allows toggling between two circuits or states by connecting the input to either of the two outputs.

Double-Pole, Single-Throw (DPST) Incorporates two input terminals and two output terminals, simultaneously opening or closing two separate circuits.

Double-Pole, Double-Throw switches (DPDT) Similar to SPDT but with two input and two output terminals, this form offers increased switching options by connecting each input to one of two outputs.

Switches are also available with many operating behaviors, including:

Momentary switches return to the default state, which can be either open or closed, when released, like a doorbell.

Latching or maintaining contactswitches retain the switch position until manually changed, like a light switch.

Toggle switches are operated by flipping a lever to toggle between open and closed positions, providing a straightforward on-off control mechanism.

Selector switches have multiple positions to permit users to choose from different settings or options.

Relays are switches that can be operated remotely by means of an electromagnet. Relays are used in control circuits and may be operated either manually or by automation.

Contactors are relays designed to handle higher voltages and currents than typical switches or relays, making them suitable for controlling heavy loads, such as motors, heaters, and other heavy-duty equipment.