18th May 2022

What is a Circular Connector?

What is a Circular Connector?

What is a Circular Connector?

A circular connector is composed of two parts – a cylindrical, multi-pin male plug and female receptacle with corresponding sockets that when mated with each other is designed to power electrical devices or transmit electrical signals. Their circular design is effective in withstanding harsh environments and can reliably deliver both data and power. From the International Space Station moving at 7.66 km/s around the Earth, astronauts looking through its cupola at the continents down below, to fighter jets and passenger aircraft flying high above the clouds, to nuclear powered submarines that lurk in the icy depths of the arctic ocean and subsea internet cables that trail across ocean floors, circular connectors deliver crucial electrical signals and power to massive machines operating in harsh environments that must be fail safe and dependable.

Enabling A Central Nervous System For Machines

These circular connectors and cables act like the nerves and blood vessels that deliver feeling and strength to our bodies. They are like nodes in the central nervous systems of aircraft, wind turbines, tidal turbines, expansive solar farms, marine vessels, trucks and trains. These cannot afford to fail in the harsh environments that they operate, otherwise catastrophe awaits. They are ‘fit and forget’ technology that can be relied on to perform their function whether underwater, pounded by wind, waves and vibrations or exposed to extreme pressures, the freezing cold or searing heat. But aside from space stations, fighter jets and large passenger planes, submersibles moving slowly in the dark and deep-sea mining robots lumbering across ocean floors in the search for rare earth minerals for our phones and EVs, most circular connectors are used in the vast array of factories and industries on land that deliver the power, data, warmth, food and products that we so desperately need. But what are circular connectors actually made up of?

Shells, Inserts, Contacts And Backshells

Circular connectors as judged by their name consist of two circular parts, a multi-pin male plug and a multi-socket female receptacle. In the male plug a circular shell made from plastic or metal encases an insulating insert which in turn orientates electrical contacts or pins. The female receptacle contains the corresponding sockets that the pins mate or connect with. The shell diameters range in size from nanominiature circular shells a few millimetres across to those 50 mm in diameter or more. Larger shell sizes are generally used to house larger contacts used for power or more contacts whereas smaller shells are designed to house the smaller contacts needed for sensors.


The cylindrical housing and circular contact interface geometries allow for easier engagement and disengagement, tight environmental sealing, and rugged mechanical performance. The male plug of the connector containing the pins plugs into the female receptacle containing the sockets. They are especially resistant to environmental interference and accidental decoupling through the use of screw, bayonet, twist-lock and push-pull mating styles and can be sealed to IP67 or higher.


When the male plug and female receptacle are pushed together and make contact electrical current flows through the electrical contacts that are made from high-conductivity, oxidation-resistant materials like brass and steel. These can be bare or plated in gold and/or silver to offer better conductivity for lower voltages and currents. They are usually attached to each wire strand within the cable using solder or screw fittings or by using a crimping tool, which employs a solderless crimp mechanism. Each contact is passed through the circular connector housing and insert before the connector backshell is closed. In the case of a crimp fitting individual contacts can be replaced without requiring the entire connector having to be replaced.


Circular connectors commonly use backshells, which provide physical and electromagnetic protection as well as also providing a method for locking the connector into a receptacle which provides stress relief for the attached cable. In some cases this backshell provides a hermetic seal or some degree of ingress protection. As well as protecting the multi pin circular connector and cable link from physical stress like strain, shock or vibration, backshells can also stop any electromagnetic interference that can occur when lightning strikes an aircraft or wind turbine tower. Backshells are also known as endbells, strain-relief clamps or cable clamps.


Circular connectors are designed to mount in-line on a cable end or directly to panels, circuit boards or other entry points. There are several methods for affixing the connector including the use of bulkheads, jam nuts and flange mounts. The two most widely used circular connector mounting types are jam nuts and flange mounts. A jam nut uses a large hex nut to screw onto the connector’s threads and is used in applications with space constraints. A flange mount has a protruding ridge, lip or rim that is bolted onto panels or other entry points that serves to increase strength.

Hybrids And Medical Environments

In medical environments where crucial life support systems and ventilators are connected up to patients, time cannot be wasted in searching for the correct cable in the event of a medical device misconnection in complicated systems. Hybrid connectors are the perfect solution to this predicament as they can connect high voltages, optical links, fluids, power and signal lines through a single connector. Hybrid connectors often consist of a rectangular plug that itself contains several circular connectors which enables clinicians to connect complex medical equipment efficiently and quickly. Keyed circular connectors with different colours and sizes can also make it impossible to connect the wrong cable.

The Circular Enablers of The Industrial Internet Of Things

Circular connectors come in a range of shell sizes but the rugged and durable M12 connectors have a long history of use in industry long before The Internet was a thing. However now that The Fourth Industrial Revolution (Industry 4.0) or the Industrial Internet of Things (IIoT) is currently underway they have become the preferred connector for Industrial Ethernet. Designers and original equipment manufacturers (OEMs) are incorporating M12 connectors into new machines as industrial environments become ever more connected. They are also using these connectors to update existing infrastructure. Using M12s to replace older and less robust technology is relatively simple and cost-effective because of their backward compatibility.

How can Live Electronics support different industries with circular connectors ?

Here at Live Electronics we are continually looking for the best products at the best price to help with modern technologies such as circular connectors. We supply IP68 rated waterproof, highly robust and high voltage/current connectors all the way down to 6mm low voltage connectors. Different mating styles range from screw and twist-lock to bayonet and push-pull. We also supply hybrid connectors which are ideal for connecting both power and signal circuits through a single connector. With many different choices available please feel free to contact us to discuss your requirements, we are always happy to help.


A circular connector provides a robust and failsafe connection to supply electrical signals, data and power. Circular power, data, fibre and automation connectors are used in a range of demanding environments both on land and at sea.


Circular connectors are used in critical areas such as the military, aerospace, hospitals as well as hostile environments. In industry they are used in test, measurement and automation technology. They are also used in sound engineering and radio communication. In 5G mobile communications they are used to connect Antenna Line Devices or ALDs

The shell of a circular connector is made from plastic, metal or moulded rubber and the insert from a moulded piece of resilient dielectric material. The contacts are made from high-conductivity, oxidation-resistant materials like brass and steel. These can be bare or plated in gold and/or silver to offer better conductivity for lower voltages and currents.