# What do the symbols on an electrical switch mean?

• AbdullahS
In summary, the conversation discussed the meaning of a symbol in a circuit, which was identified as a switch with an "x" indicating the opened contact. The symbol also included a circuit breaker and a heater, which are used to indicate the circuit breaker's thermal activation and trip point rating. This functionality is commonly used for loads with high inrush current, such as motors.
AbdullahS
Hi All,

I am just trying to understand a circuit but cannot figure out the meaning of the following symbol. Did not get very far from googling electrical symbols.

The symbol is given below. I know it is a switch but what does "x" mean on one of the wires and what do the half sine and square waves mean on the other wire?

Thanks you very much for any help that you can offer.

Regards,
Abdullah

The 'half sine' and square wave indicate respectively: a Circuit Breaker and a Heater.
The heater is sometimes shown as a resistor symbol as in this drawing.

The "10A" is the circuit breaker trip point rating and the heater indicates the circuit breaker is thermally activated.

As a guess, the X indicates the switch contact that is opened when the breaker trips. This would typically be the Hot lead of the incoming power, as opposed to the Neutral lead.

This general functionality is used as a time-delay trip for loads with high inrush (start-up) current, such as motors. The thermally activated breaker takes a bit of time to heat up and trip, allowing the high inrush current for the short time needed for the motor to get up to speed. If the current stays high, as when the motor is overloaded or fails to start, the breaker heats up, trips, and disconnects from the incoming power.

Cheers,
Tom

scottdave, hutchphd, AbdullahS and 1 other person
Thanks Tom!

Tom.G

## 1. What do the "on" and "off" symbols on an electrical switch mean?

The "on" symbol on an electrical switch typically looks like a vertical line intersecting a horizontal line, while the "off" symbol is often a circle with a line through it. These symbols indicate the position of the switch - "on" means the circuit is closed and electricity can flow, while "off" means the circuit is open and electricity cannot flow.

## 2. What does the "I" and "O" symbols on an electrical switch mean?

The "I" and "O" symbols on an electrical switch are often used to indicate "on" and "off" positions, respectively. These symbols are derived from the words "input" and "output," and are commonly used on toggle switches to show the direction of current flow.

## 3. What do the "+" and "-" symbols on an electrical switch mean?

The "+" and "-" symbols on an electrical switch are used to represent positive and negative polarity, respectively. These symbols are commonly found on switches that control the direction of current flow, such as in a DC motor.

## 4. What does the "1" and "0" symbols on an electrical switch mean?

The "1" and "0" symbols on an electrical switch are often used to represent "on" and "off" positions, respectively. These symbols are commonly found on digital switches, such as those used in computer circuits.

## 5. What is the purpose of the symbols on an electrical switch?

The symbols on an electrical switch serve as a visual representation of the switch's function. They indicate the position of the switch and the direction of current flow, helping to ensure that the switch is used correctly and safely. These symbols are standardized and universally recognized, making it easier for individuals to understand and operate electrical switches.

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