Of the annual global connector volume of around 35 billion dollars, roughly 60% can probably be attributed to standard connectors (such as D-Sub, RJ 45, USB, DIN,
With these standardised connectors, compatibility can also be assumed, except in the case of aberrations.
The question that arises with the remaining connectors, regarding the manufacturers own developments documented in catalogues and customized developments, is:
How can non-standard connectors, whose manufacturers have no license agreement with each other, be plug-compatible?
Types of compatibility:
In conjunction with the compatibility or interchangeability of connectors, a distinction is made between:
- Parts compatibility
- Assembly compatibility
- Plug compatibility (also called interface compatibility)
- Functional compatibility
In addition, there is also the important concept of
Forward and backward compatibility also called cross compatibility
As a rule, parts compatibility does not play a role. Cable collets, shielding rings, contacts, etc., do not have to be identical. The user utilises complete products.
Ensuring assembly compatibility is usually uncomplicated. The dimensions here are relatively approximate, because each connector manufacturer must define the interfaces in such a way that the housing supplier or PCB supplier can cope with the specifications.
Every other connector manufacturer can also obtain these specifications and take them into account.
The crucial point is the question of plug compatibility and functional compatibility.
With connectors, there are always pairs that belong together, namely, plugs and receptacles.
The term plug compatibility means that the plug (or receptacle) from manufacturer A can be replaced by the plug (or receptacle) of manufacturer B.
In this view, the possibility of mechanical insertion is emphasized, meaning the locking mechanism, the pole image of the insulator, the contact diameter and even the coding.
In the broader sense, functional compatibility means that the cross-paired connectors from manufacturers A and B meet the same requirements as the purebred connectors from manufacturer A.
This includes not only such values as volume resistance or mating forces, but also environmental conditions, such as humidity and the temperature, radiation and shock loads.
This also includes safety functions that are given by codings: if the coding is missing, two connectors could easily be plug compatible without the safety function being guaranteed.
Copy, develop, improve?
In the exchange terminal, ODU has long been delivering many thousands of plug pairs developed to custom specifications a month.
It is obvious that with a telecom project of this magnitude, competitors are attempting to get in on the business. To get right to the point: the attempts have failed until now.
How could compatible plugs be developed under the conditions mentioned here (no standardisation, no license exchange)?
The starting point is always a sample part.
It is better to have a pair and even better to have several pairs - including some from different production lots.
The sample part can be obtained on the market or, in the case of customised developments, from the user (who is generally interested in finding a second source).
The sample part is measured using measurement machines that have precision optical systems, lasers and sensing devices and that today work in the µm range.
Specifically, some of the dimensions measured are: housingÆ, insulation bodyÆ, contactÆ, reference circle and angle arrangement of contacts, angle positioning of the coding, etc.
In addition, insertion and withdrawal forces can and must be determined and electrical measurements must be made: volume resistance, contact point, screening attenuation, and others. This applies to single contacts and to complete inserts.
Furthermore, the materials must be determined, with the surface materials having the potential of being particularly problematic.
But even with all of the described measures, no matter how carefully planned and performed, one cannot escape the fact that only one sample was measured.
One can obtain several samples, but then the result is a series of measurements with averages and distributions. Nevertheless, the fact remains: one obtains actual values, but does not know the nominal dimensions and the range of the tolerance fields.
Added to this: there is also measurement errors and even production errors at the manufacturer. Then how is it possible to come up with a compatible connector?
And nevertheless, they still work.
In spite of incomplete information and diverse risks, there are considerations and measures that allow connectors to be produced that prove to be compatible in practice:
- The manufacturers proceed rationally: for example, for a 6-pin insert, a subdivision of 6 x 60° (and not first 59° and then 61°) is usually selected. And, as a rule, round numbers are chosen for the nominal sizes (such as pin Æ is 0.7 and not 0.68)
- The production quality of renowned firms is high: turned parts are produced with small tolerances (the 0.7 pin at ODU, for example, with 0.7 + 0 - 0.02 mm), clearly far from the tolerances that the function would allow.
- Moulded articles, even from different recesses, are inevitably reproduced identically and with a high level of precision.
- Over time, there are feedback and optimisation possibilities: even if a manufacturer delivers tens of thousands of finished products, it still falls back on the same housings or contacts over and over again. This increases the database, and therefore the certainty.
- There are intelligent possibilities for verification and optimisation: to be stressed are the determination of the insertion and withdrawal forces (for single contacts and complete inserts and complete connectors), the volume resistances and the contact points.
All of these and others, combined with mating cycle tests and, above all, with cross tests.
For years, ODU has been delivering many millions of Push-Pull connectors a year.
Many of these connectors replace competitive products in the current series or are used in parallel with competitive products.
In this process, no error rates have been observed that differ significantly from error rates for purebred combinations.
Well-known manufacturers around the world confirm that the compatibility is practically a given, in that they specify the products from ODU together with the corresponding products of the competition in the parts list.
These standardised connectors are available from Clarke & Severn Electronics .