Connector sex

Updated October 8, 2005

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Heh heh... he said, like sex...

A common misconception is that the sex of a connector has something to do with the outer connector. WRONG! The sex of the connector refers only to the inner conductor.

With the notable exception of the "sexless" 7 mm connector, connectors are come in matched pairs. The term "male" implies a connector where the center conductor protrudes, while the term "female" implies a connector where the center connector forms a sleeve around its male counterpart. Alternative terms are "plug" for male, and "jack" for female.

Reverse polarity connectors

Reverse polarity connectors are ones in which the sex is the opposite of what you'd expect. Reverse polarity connectors are sometimes used in an attempt to "key" connections so that incorrect connections are not possible. These are available from major connector manufacturers as catalog items.

Here's a comment from our message board about reverse-sex connectors: "FCC rules have led to a proliferation in the use of reverse sexed RF connectors. For unlicensed users there is a requirement that the manufacture must ensure that unauthorized antennas cannot be connected to the equipment. That is why all WIFI equipment with connectorized antennas use reversed sex connectors. Cisco uses RP-TNC, Netgear RP-SMA, and Symbol Technologies RP-BNC for their 802.11b/g (2.4GHz) WIFI radios and access points." Yikes, we didn't know that these were being proliferated!

In a lab environment, we recommend that you never use these, because it doesn't prevent connections, any idiot can jam reverse-polarity male connectors onto normal male connectors and mess them both up. If you want to make something idiot proof, perhaps you should look at reverse threads for certain connectors (which are also available from major connector manufacturers).

In the picture below are three SSMA connectors. The connector on the left is the normal SSMA male, while the one on the bottom is the normal female. On the upper right is a reverse-polarity male connector, it has the normal male pin inside, but has the external threads of a female connector. If you look closely, the center pin is bent on the reverse polarity connector; chances are that the technician that "owns" this connector doesn't even know it is reverse polarity. Such a connector is useless if you don't have the opposite reverse-polarity female connector to mate with it. Jammed into a normal male SSMA male connector, it probably makes contact, even if the two male pins are bent against each other (but it won't be a great fifty-ohm match at high frequencies!) Whenever you find such a connector, put it in a specially-labeled box, or just throw it out!