There are a lot of connectors we use in our work, no doubt about that. Sometimes the variety is due to the technical demands of the application—DC, AC power, audio, data, RF, microwave, and so on–and sometimes it is because a vendor prefers a proprietary connector to lock you in to their cables and accessories.Other connectors have physical form-factor differences, depending on the way the cable exits or the strain-relief options.
Regardless of the reason, one of the most frustrating situations for engineers, especially when in prototype or debug phase, is when you don’t have the right connector to mate cable and unit.
One way to deal with this is to make up a special cable, using the appropriate matching connectors at each end. But that brings new problems, assuming you have the correct mates and you don’t need special tooling to attach the connector to the cable: many high-performance cables are complex assembles, and at higher frequencies, they are transmission lines with impedance-matching and discontinuity issues.
The more elegant solution, of course, is an adapter connector designed for the specific pairing you are trying to resolve, or the physical constraints you face. I suspect that many of you have a drawer or box with a collection of these odd pairings. For example, I have an RP-SMA to RP-TNC adapter which came with my D-Link ANT24-0700 external 802.11 antenna (an accessory which “saved the day” for me, see here.). Turns out I didn’t need the adapter, but someday it may solve an RF-connector mating problem I can't anticipate—yet.
I also have some adapters which I picked up at flea markets, and which are so elegant and nicely machined in their own special ways, that I couldn’t resist them.Go to the web site—or even better, the print catalog—of almost any RF cable/connector vendor, and you'll see many of these works of “art” that were developed and tooled to meet someone's need.
Even the ubiquitous and fairly limited slate of connectors in the USB family has adapters. For example, if you are using the very common mini-USB connector for your phone, camera, or GPS, and you get a newer device which sports the micro-USB, you can get a mini-to-micro transition adapter (so you can use all your USB-charging cables and wall-warts) for about $3. Or if your installation is physically cramped, you can get a right-angle USB connector adapter:
For basic AC-line power, if you want to use the standard Edison-socket-based LED or CFL bulb in a candelabra socket, you’ll need this fairly obscure adapter:
What’s the most interesting or strangest adapter pairing you’ve seen? Is there one you’d like to have—but haven’t been able to find yet??