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Dual USB-C
Small devices use two-prong USB-AC, but there's also a three-prong version with a USB-B plug as the ground.
Title text: Small devices use two-prong USB-AC, but there's also a three-prong version with a USB-B plug as the ground.

Explanation

Ambox notice.png This explanation may be incomplete or incorrect: Created by a USB-DC PLUG. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.

This comic shows Cursed Connectors #187, indicating that there are many very bad types of connectors and that this comic could be the first in a series of Cursed Connectors, just like the Bad Map Projections series. Only time will tell if this actually becomes a series as with the map projections.

USB-C connectors are the newest version of the USB standard, and were controversial on launch[citation needed] for reasons Randall previously covered in 927: Standards. Randall proposes a new type of connector which would see two USB plugs side-by-side able to be inserted simultaneously by housing them inside a NEMA 1-15P plug, more commonly known as a Type A plug, that is usually used in some countries to connect electrical devices to AC current. This does not seem to offer any advantages other than reviving the controversy.

Further, the plug introduces several disadvantages, including, but not limited to

  • The plug creates the risk of accidentally plugging a USB-C device into a power outlet, which is likely to damage the device as the voltage of a NEMA 1 circuit is about six times as large as the maximum for USB-C. Additionally, mains power outlets typically supply alternating current, whilst USB devices operate on direct current, which is also likely to result in damage to the device.
  • The outer metal casings of the plugs are usually connected to the device's ground plane, so the casings likely have a low-resistance path between them. Plugging such a device into a power outlet would form a short circuit.
  • The plug likely won't fit a power outlet (NEMA plug pins have a 6.4×1.5 mm cross-section and the USB-C is 8.4×2.6 mm.)
  • Any device meant to be connected to the full plug would need vertical ports, making any theoretical device quite thick.
  • The plug could occupy 6+ ports of a USB-C hub with vertical ports, taking up the space to charge 2-6 phones with a single device.
  • The plug being mimicked is typically not found in a double male configuration implying that the cord is attached to a device at the other end in a non removable way (Typically, the other end of detachable power cords for appliances is one of the plugs specified in the IEC 60320 standard, so presumably for Randall's connector application would substitute USB-C sockets in a C9 or similar configuration.)

The connector therefore is considered cursed.

Notably, there's an existing dual USB-C plug in use for Macbook-compatible high-performance dongles, among other things, which is remarkably similar but avoids all the above disadvantages.

The title text indicates that an equivalent for the 3-pronged NEMA 5-15P plug (a.k.a the Type B plug) for AC current could be created easily by incorporating a USB-B plug, which are small and square-shaped and could therefore function as the ground prong. There appears to be no reason to do this other than because both names contain the letter 'B'.

Unconventional uses for electric plugs are a recurring topic in xkcd (see 1293: Job Interview and 1395: Power Cord). Combining them with USB was previously explored in 1406: Universal Converter Box among other combinations.

Transcript

[A power cord like plug with two prongs is shown, but each prong is in the shape of USB-C connectors. Above is a title and below is a label.]
Cursed Connectors #187
Dual USB-C


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