Rocker Switch Terminology

Rocker Switch Terminology

Rocker switches are common in various industries, including boating, 4x4 vehicles, and caravans, offering a convenient way to control electrical systems. Understanding the different terms associated with rocker switches is essential for selecting the right switch for specific applications. In this blog, we'll explore the key terms used to describe rocker switches, including SPST, SPDT, DPST, and DPDT. We'll delve into their meanings, provide examples, and discuss their relevance in the boating, 4x4, and caravan industries.

Before we start diving into the switches themselves, lets take a look at what poles and throws are.

What is a pole?

In a 12V switch application, a pole refers to the number of separate circuits or paths that the switch can control. Each pole represents an independent circuit within the switch. For example, a single-pole switch (SP) controls one circuit, while a double-pole switch (DP) controls two separate circuits.

What is a throw?

In a 12V switch application, a throw refers to the number of positions or states in which the switch can be configured. It describes how many different paths the switch can connect or disconnect within a circuit. Common throws include single throw (ST) and double throw (DT). For example, a single throw switch (ST) has only two positions: on and off, while a double throw switch (DT) can have three positions: on, off, and on in a different circuit. The throw of a switch determines its versatility and functionality in controlling electrical circuits.

SPST (Single Pole, Single Throw):

An SPST rocker switch has a single input and controls a single circuit. It has two positions: on and off. An example of an SPST rocker switch is a basic light switch, where flipping the switch either connects or disconnects the circuit to turn the light on or off. In the boating industry, SPST rocker switches are commonly used for simple on/off functions like controlling deck wash or deck lights.

SPDT (Single Pole, Double Throw):

An SPDT rocker switch also has a single input but controls two circuits. It typically has three positions: on, off, and on. This type of switch allows for the control of two different devices with one switch. For example, in a boat, an SPDT rocker switch might be used to control a bilge pump, with the centre position turning off, the top being auto “on” and lower position being manual “on”. This gives the user flexibility in what setting they use they bilge pump in.

DPST (Double Pole, Single Throw):

A DPST rocker switch has two inputs and controls a single circuit. It has two positions: on and off. This type of switch provides redundancy and can handle higher currents than SPST switches. It can connect two inputs to one output, but never connect the two inputs to each other. In the 4x4 industry, DPST rocker switches might be used to control the power input coming from the starting battery or a secondary battery. This could be helpful as an emergency if you need to start your vehicle from your auxiliary battery.   

DPDT (Double Pole, Double Throw):

A DPDT rocker switch has two inputs and controls two circuits. It has six terminals and three positions: on-on or on-off-on. DPDT switches offer versatility and can be used for various applications requiring the control of multiple devices. For instance, in a boating industry, a DPDT rocker switch could be utilized to control the anchor winch, allowing the upper circuit to activate the free spool and the lower circuit to winch in.

Understanding the terminology associated with rocker switches is crucial for selecting the right switch for specific applications for your boat, 4x4, and caravan. Whether it's the simplicity of an SPST switch or the versatility of a DPDT switch, each type serves a unique purpose. By grasping the distinctions between SPST, SPDT, DPST, and DPDT rocker switches, you can ensure optimal functionality and safety in your electrical setup.