Locking and Retention Features
A ring-shaped 'locking detent' or 'high-retention feature', present on the barrel of some DC coaxial connectors, is a feature intended to prevent accidental disconnection. Its presence or absence can cause confusion when distinguishing very similar sizes and variants. Some of the sizes listed appear to always include a high-retention feature, while others include it only in designs from certain manufacturers. Typically, this feature is a conical cut-back section of the tip, just behind the insulator that separates the inner from outer contact surfaces. In particular, the EIAJ (JEITA RC-5320A) standard connectors appear to specify a high-retention design.
The preceding very common feature must not be confused with the much-less-prevalent 'lock-ring DC coaxial connector' which uses a captive threaded ring or collar to secure the connection between the plug and jack. Manufacturers known to offer this variant on at least some connectors include CUI, Kobiconn, Philmore, and Switchcraft. Note that this design requires that the lock-ring threading size be compatible with sufficiently protruding threads on a mating panel jack, and that some manufacturers (notably Switchcraft) have used a mix of metric and inch dimensioning. The lock-ring design, when fully engaged, offers strong resistance to unplugging; it is so secure that if the power cord is accidentally pulled forcefully, severe mechanical damage to equipment is likely.
An alternate design, the even rarer 'lock-tab DC coaxial connector' (also called 'bayonet lock') offers a compromise that resists unplugging, but which will disengage when pulled hard enough. This connector uses small metal tab protrusions on the connector barrel to lock the plug in place, requiring a special push-and-rotate motion to engage the locks. This is a mechanical way to provide a "safe breakaway" feature somewhat like the magnetic latch used in the Apple Inc. proprietary MagSafe design. Kobiconn and Lumberg have offered some lock-tab variants, and there may be other manufacturers as well.
To ensure that locking connectors operate properly, it is important to specify and to test this feature. It is likely that mating connectors from a single manufacturer will interlock correctly, but even in this case, compatibility should be verified.
A completely different series of locking connectors is the snap and lock DC connector, which is not a coaxial power connector, and is covered in a separate article on DC connectors. These multi-pin DC power connectors typically have 3 or 4 or more pins, and somewhat resemble mini-DIN connectors, except that the connector pins are thicker, to carry more current.
Read more about this topic: Coaxial Power Connector
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