Plugs for sockets, standardised charging cables or proprietary travel adapters, as well as USB sockets and much more: the number of plug types on the market is immense. Plug systems connect data, power or signal lines with each other, whereby the basic forms are almost always plugs and sockets that belong together. They are available for private use as well as for installation in motor vehicles and for use in trade and industry, where particularly high demands are often placed on performance and robustness. The following guide deals with the question: Which plugs are available? It shows different types of cable connectors to make it easier to select the right connectors for the various purposes. Variants such as circular connectors, solar connectors and automotive connectors as well as categories such as industrial connectors are discussed.
Plugs and sockets overview
Almost all cable connectors (with the exception of fibre optic cables) consist of a plug with pins and a socket or fixed socket with corresponding openings for the contacts. This ensures that the plug can be inserted into the socket - regardless of whether it is a travel adapter or an XLR plug. The socket is therefore something like the socket for connecting household appliances in households. The plug with its pins is therefore referred to as the male part of a connector, while the socket is the female part. The number of pins varies greatly between the different connector systems. In the M12 connectors alone (group of circular connectors), there are variants with two pins, but also with up to 12 pins that can be connected to conductors.
Industrial connectors
Industrial connectors can be categorised into signal, data and power connectors,depending on the type of transmission . Hybrid connectors combine different transmissions and are used, for example, for power supply and data transmission. Depending on the use, a distinction can be made between sensor and valve connectors, for example, and rectangular and CEE connectors> depending on the design. Industrial connectors are used, for example, in the automation of production processes, but also in wind energy or ship and railway logistics.
The basic requirements for industrial connectors are set out in Part 1 of IEC 60309, while Part 2 of the standard defines the special properties of CEE high-current connectors.
Circular connectors
Circular connectors are characterised by their cylindrical shape. As circular connectors are also robust connector types, they are often used as industrial connectors. Circular connectors include the connector types M5 to M58, which are labelled with the letter "M" and a number, where the "M" stands for "metric thread" and the number for the threaded diameter. Traditionally, the socket and plug are screwed together, although push-pull systems are now also available. They enable a quicker and tool-free connection of socket and plug.
Today, types such as M12 represent a large number of different plugs and sockets, so they are categorised into subgroups by coding. M12 is available in A, B and X coding, among others. The codes help to ensure that plugs and sockets that do not belong together are not connected.
The codes sometimes include several variants of the connector with a different number of pins. If you look at plugs and sockets in an overview, it becomes clear that the A coding of M12 connectors in particular covers quite a large number of connectors. In addition to the circular connectors mentioned so far, there are others as RD24, R15 and 7/8 inch. Circular connectors (depending on the type) can be used for data, signal or power transmission.
Serial, parallel & network connectors
Serial, parallel & network connectors are connector types known primarily from IT. The words "serial" and "parallel" describe the type of data transmission. In the parallel variant, bits are transmitted in parallel on several wires. The serial variant transmits bits one after the other instead and there are corresponding connector types for both variants.
The best-known connectors include the trapezoidal D-Sub connectors, which exist in variants with different numbers of pins. Some are serial, others parallel connectors. The relevant standard for these connectors in Germany is DIN ISO 41652-1. Other relevant connector types in connection with serial and parallel interfaces are the Rj45 connectors, which are familiar from network cables. They are classic network connectors. PS2 plugs, for example, are used to connect peripheral devices such as a mouse or keyboard, but are now often replaced by USB plugs.
Automotive connectors
Parking aids, anti-lock braking systems, electronically controlled airbags: the number of electrical components in motor vehicles has increased significantly in recent decades. And of course special connectors are required in this environment. Amphenol A series connectors, for example, play an important role here. These plugs are robust and waterproof connector systems for harsh environments.
Three subgroups are particularly relevant in automotive technology: the AT, ATM and ATP series. They remain intact even in the event of major vibrations, withstand temperatures well above 100 degrees and up to 50 degrees below zero and are UV-resistant. These are all important properties for automotive connectors.
AT series connectors allow up to 13 amps of current per contact and are available in two to 12-pin variants. The ATM group consists of rectangular connectors that are especially suitable as connectors for smaller connection cross-sections. The ATP series of connectors offers a particularly high level of sealing. Compared to the AT series, it is also designed for larger cable diameters and can transmit higher currents.
Electric cars
Plugs for charging cables used to charge electric vehicles are now also important in the automotive sector. The type 2 plug is widely used in Europe, while single-phase type 1 plugs are more common in Asia. CCS plugs are used for the charging cable at DC fast-charging stations.
Solar connector
While you can easily connect a balcony power plant to a socket using a Schuko plug or Wieland connectors, MC4 connectors play a major role in the installation of rooftop photovoltaic systems (PV systems). In this context, "MC" stands for the former Swiss company Multi-Contact, which has been part of Stäubli since 2002. MC4 pl ugs are one of the most frequently used plug types in PV systems with the corresponding sockets. Their properties include high temperature stability and low contact resistance. Both prevent efficiency losses in the system and excessive heating of the solar plugs. Special solar cables must be used to connect these plugs.
Data connectors
Of course, there are many different data connectors, as the look at serial and parallel interfaces in IT has shown. However, one connector family is particularly prominent and should therefore be mentioned separately. We are talking about USB connectors. USB is the abbreviation for "Universal Serial Bus".
USB 1.0 was created in 1996, but no longer plays a role today. USB 2.0 has been around since the turn of the millennium. It enables transfer rates of 480 Mbit/sec. USB 3.0 then brought transfer rates of five Gbit/s from 2008 and data transfer became even faster with connector variants such as 3.1 and 3.2.
USB plugs also differ in terms of their design. Type A plugs are the classic type. Type B was used for printers and scanners, for example, but is now often replaced by type C. Mini and micro USB plugs are miniaturised versions of the USB plug family. However, USB is not only a global standard for data transfer. USB has become indispensable, particularly as a plug type for charging cables or as a multifunctional socket in a travel adapter, for example for charging smartphones.
Video/graphics connectors
VGA connector, HDMI connector: These are well-known connectors from the video and graphics sector. The VGA connector was the standard for a long time, but is now considered obsolete. VGA connectors transmit analogue signals, which means that digital signals have to be converted, resulting in a loss of quality. In addition, VGA connectors only transmit image signals, whereas HDMI, for example, transmits audio and image.
DVI (Digital Visual Interface) connectors also belong to the video and graphics connectors. DVI-A only transmits analogue signals, DVI-D only digital, while DVI-I can transmit both types of signal. Other variants of video and graphics connectors are Thunderbolt and Display Port connectors.
The quality of the connectors can be assessed based on the maximum possible data rate and image resolution. An example: HDMI 1.0 managed a maximum data rate of 3.96 Gbit/s. HDMI Ultra-High-Speed achieves 48 Gbit/s. And while HDMI 1.0 was designed for a maximum resolution of 1920 × 1080p, version 1.2 was already capable of 2560 × 1440p.
AV connectors
AV connectors are audio-video connectors, i.e. connectors that transmit audio and/or video signals. They include the SCART connector, the former standard for connecting devices such as TV sets and video recorders. However, these analogue signal-transmitting connectors are now largely considered obsolete.
RCA plugs are usually available in pairs, for example as audio cables, where one plug transmits the left channel and the other the right channel. Other AV connectors for the audio sector are jack plugs in smaller (2.5 mm) and larger (6.35 mm) versions. The latter are primarily intended for commercial and professional applications. The same applies to XLR connectors, which can transmit digital and analogue audio signals.
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