Switches and Contacts Essentials
This technical article delves into a diverse array of switches and components that are fundamental to the operation and control of electrical systems. Starting with the basics like TURN, PULL, and PUSH switches, we navigate through the intricacies of latching switches and emergency stop switches, exploring their applications and functionalities in various contexts.

As we progress, the article unfolds the concept of Passing Contacts and the unique characteristics of Normally-Open, Timed-Closed, and Normally-Open, Timed-Open Contacts, shedding light on their importance in specific control scenarios.
The transformative role of solenoids in converting electrical energy into mechanical motion is also explored, showcasing their versatility in modern control systems.
In the latter sections, the focus shifts to more advanced components such as CAM-operated change-over switches, Terminals with fuses, and Multi-pin connectors (male and female). The detailed exploration of the Harting Plug, a connector vital in gas-insulated substations, serves as a culmination of our journey through the realm of electrical switches and components.
Ok, so let’s dive into details!
- TURN Switch
- PULL Switch
- PUSH Switch
- Latching Switch
- Emergency Stop Switch
- Passing Contacts
- Normally-Open, Timed-Closed Contact
- Normally-Open, Timed-Open Contact
- Solenoids: Transforming Electrical Energy into Mechanical Motion
- Change-Over Contact
- Binary Inputs
- AC Socket
- Gang Operation of MCB or Circuit Breaker in Schematics
- CAM Operated Change Over Switch
- Terminal With Fuse
- Multi-Pin Connector Male and Female
- Harting Plug
1. TURN Switch
A TURN switch, also known as a rotary switch, is a type of switch that operates by rotating a control knob. It is commonly used to select between different positions or settings in a circuit. The switch typically has multiple contact points arranged in a circular or semi-circular pattern. As the knob is turned, the movable contact arm makes contact with different fixed contacts, thereby establishing or breaking electrical connections.
In a schematic diagram, a TURN switch is represented by a circle with an arrow indicating the rotational direction. The number of positions and the specific connections associated with each position are detailed in the schematic symbols.
Figure 1 – Representation of the turn switch contacts in schematics


2. PULL Switch
A PULL switch is a type of switch that is activated by pulling or tugging on a control mechanism. These switches are often used in devices where a direct and manual action is required to toggle the switch between its ON and OFF states. PULL switches are commonly found in applications like lamps, ceiling fans, or simple devices where a physical pull or tug is convenient for user interaction.
PULL switches might also have additional features, such as multiple positions or intermediate states, depending on the design and intended functionality.
Figure 2 – Pull button (left) and switch (right) with normally closed contact


3. PUSH Switch
A PUSH switch, also known as a momentary switch, is a type of switch that is designed to make or break a connection temporarily when pressure is applied to its actuator. Unlike toggle switches that have a latching mechanism, a PUSH switch returns to its original state when the force is released.
These switches are commonly used in applications where a brief and momentary action is required, such as in push-button controls, doorbells, or as the activation switch for electronic devices.
PUSH switches can come in various configurations, including normally open (NO) or normally closed (NC), depending on whether the switch’s default state is open or closed, respectively.
The specific functionality of the switch in a circuit is detailed in the schematic symbol.
Figure 3 – Representation of push button with normally closed contact in schematics


Figure 4 – Representation of push button with normally open contact in schematics


Figure 5 – Push button with key and normally closed contact


Figure 6 – NFPA Symbol representation of the push button with normally closed contact


Figure 7 – NFPA Symbol representation of the normally open contact


Figure 8 – NFPA Symbol representation of the normally closed contact


4. Latching Switch
A LATCH switch, also known as a toggle or flip-flop switch, is a type of switch that maintains its state (either ON or OFF) after being toggled until explicitly changed. Unlike momentary switches, which return to their default state when the force is released, latch switches retain their position until another action is taken.
These switches are commonly used in applications where a stable and persistent state is required, such as power controls in electronic devices, light switches, or any scenario where maintaining a specific state is crucial. In a schematic diagram, a LATCH switch is typically represented by a rectangle or another shape with a distinctive toggled arrow or line indicating its toggle action.
Variations of latch switches include those with momentary actions to set or reset the latch, and they may have multiple poles and throws to control multiple circuits simultaneously.