What exactly is a Nexus plug and what does the pin wiring of this plug look like?

The Nexus connector has now become the standard connector for accessories such as headsets and headsets for radio equipment. The 4-pin connector originally comes from the aviation and aeronautical radio/flight intercom sector, where it is still used today under the designations U174/U, U93A/U and, for sockets, U92A/U as an interface to the intercom for voice communication, e.g. in helicopters with the Nexus 03 assignment (historically due to aviation headsets from David Clark).

In addition to the above designations, the name Amphenol TP120 is also used, and very often incorrectly in normal usage, the term “NATO plug” is also used. This is because these plugs are also used in the military sector for tactical headsets.  For these applications, especially with Peltor headsets, there are usually two versions, namely the Peltor assignment (Nexus 02) and the NATO assignment (Nexus 03, sometimes also referred to as David Clark pinout or NATO US), with the NATO pinout becoming increasingly prevalent, not only in the military sector, but also in the police force. At Peltor, the plug is also referred to as J11.

Why is the correct pin assignment so important?

Headsets with Nexus connectors usually require, except in the intercom area, a corresponding PTT transmit button base equipped with the appropriate connector for the respective radio device when used with radio devices for better application.

This can be a simple talk button with a Nexus socket (as well as a cable with a Nexus coupling) or, for example, a handheld monophone with a Nexus socket. The sockets must now be equipped with the same pin assignment as the headsets to ensure proper functioning. In the field of handheld monophones, however, there are now also so-called multi-pin devices that accept different assignments or wirings of the headsets, or recognise the pin assignment of the headset and adapt to it electronically.

The headsets therefore always have the same technical function, but if the pin assignment of the PTT base is not compatible or suitable, the headsets may not work.

Savox wiring (Nexus 01) has now become the standard in the fire and rescue services sector. This is also used by other manufacturers such as Imtradex, Titan and Ceotronics, mostly in these areas of application.

In order to still be able to use headsets with incompatible Nexus assignments, we also offer conversion to the correct assignment as well as adapter cables with Nexus plugs and Nexus couplings with correspondingly adapted wiring.

Difference between Nexus NATO (US) and NATO UK connectors

To complicate matters further, in addition to the Nexus plug, there is also the NATO UK plug, which looks relatively similar to the Nexus plug but is mechanically different. This is why there can be misunderstandings when talking about the NATO plug.
Do you mean the Nexus plug with NATO pinout or the NATO UK plug?
Visually, the plugs are difficult to distinguish. However, there are a few distinguishing features: The Nexus plug has a more rounded head, while the NATO plug is comparatively “pointier”.

Visually, the plugs are difficult to distinguish. However, there are a few distinguishing features: the Nexus plug has a rather rounded head, while the NATO plug is comparatively “pointier” and usually brass-coloured. At the end of the plug towards the shaft, the NATO UK plug has an additional insulating ring. Furthermore, the shaft of the NATO plug is usually much thicker (20 mm) than that of the Nexus plug.

However, the NATO-UK plug is far less common than the Nexus plug. If you ever encounter this problem, adapter cables are available for this purpose to match the two plugs/sockets.

Summary

There are currently three pin assignments for the Nexus connector that have become standard in different areas of application:

• Savox assignment Nexus 01 -> mainly used by fire brigades, rescue services and for standard applications
• Peltor pin assignment Nexus 02 -> used by the police and military (although the trend is declining in both cases), sometimes in industry
• NATO pin assignment Nexus 03 -> used in aviation and aeronautical radio, police and military (trend strongly increasing), mountain rescue (due to compatibility with helicopter intercom)

Wiring / Assignment / Wiring of the socket