This article relies largely or entirely on a single source. (July 2017)
Dongles were originally created in the 1970s to protect computer software which would function only if the dongle was plugged in - see the History section below.
The term is now used generically for any sort of small device or adapter plugged into a computer, games console, TV or other system. For example: WiFi adapters, Bluetooth adapters, and even USB "sticks" or "drives", are frequently referred to as dongles. Other devices include digital media players such as Amazon Fire TV Stick, Chromecast, Roku Streaming Stick, Chromebit and Intel Compute Stick.
The first software protection dongle was invented and named in 1978 by Graham Heggie, Pete Dowson and Mike Lake to protect the Wordcraft word processor running on the Commodore PET. It consisted of a 74LS165 shift register connected to the external cassette port on the rear of the PET. The 8 data lines of the shift register were connected at random to ground or 5V and Pete Dowson wrote obfuscated assembler routines to waggle a clock line to the shift register and shift bits in from it on another line. The 255 random combinations were considered sufficient protection at that time. The same design was later used to protect Wordcraft and other software products on 25 pin parallel, 25 pin serial and 9 pin serial ports on a variety of microcomputers including the IBM PC.
The name dongle arose because a strip of Veroboard was dangling from wires connected to the cassette port of a Commodore PET on Graham Heggie's kitchen table when the device was first created. "Dangle" became "dongle" after a very brief "what shall we call it?" session - with no-one called "Don Gall" involved!
The first dongles closed off the use of the port for other purposes so pass-through dongles were developed to attach to the parallel port of the IBM PC to allow normal operation of the printer. Note: IBM used a DB-25 way parallel connector, not the original 36 way Centronics connector - though the word "Centronics" had by then become a generic name for parallel ports.
- The CD-based parts catalog (known as "ETKA") used by Volkswagen Group since 2000 requires a coded dongle be plugged into a host computer's port in order to run.
- Some professional digital audio workstation packages on the Atari TOS platform required the presence of the supplied dongle in the computer's cartridge port in order to run. Steinberg's Cubase range and C-Lab's Creator and Notator packages frequently send data to the dongle, which sends a response determined by the electronics inside the cartridge.
(The additional expense of producing the dongle was justified by the high purchase price of the software (hundreds of British pounds) and the tendency for unprotected software to be subject to piracy. To ensure compatibility with MIDI and other audio expansion units that also occupy the single cartridge port, some dongles had a pass-through connector to accommodate them. Some expanders were also designed with backplane sockets to host the different dongles unique to a specific set of packages. Eventually, software pirates were able to circumvent the dongle scheme by modifying the program's binary to accept simulated dongle responses, at the expense of stability and performance.)
Copy protection circumvention
- Some unlicensed game cartridges have a "daisy chain" that allows licensed games to pass along their authorization, for instance to circumvent the 10NES chip on the Nintendo Entertainment System.
Small peripheral appliances
- Small devices that plug into other equipment to add functionality are often referred to as dongles; for example the infrared remote control adapters available for smartphones, or digital media players such as Chromecast.
- MHL. A dongle enables adaptation to legacy standards such as HDMI via conversion circuitry contained in the dongle itself. MHL dongles often allow USB connections and/or device charging as well.
- Very short cables that connect relatively large jacks to smaller plugs allowing cables to be easily installed and removed from equipment with limited space available for connectors. The Chromecast device mentioned above, for example, comes with a short HDMI extension cable to allow its use in cramped quarters. Some devices come with a permanently attached length of cable that negates the need for a short adapter cable.
- Cassette adapters enable cassette-radios to allow AUX in, like with iPod/MP3 player/smartphone (portable CD players before 2000)
- Personal FM transmitters allow content from a portable media player, portable CD player, smartphone, portable cassette player, or other portable audio system to be heard on an FM radio.
- IDE/PATA connectivity can be re-channeled with some dongles:
- Old school video game consoles:
- The Everdrive series of game cartridges has enabled classic systems such as the Sega Mega Drive and Nintendo 64 to allow one cartridge to have a number of games that were formerly on multiple cartridges of their own, by use of an SD card with ROMs on them; since it can allow a real game console to access ROMs, which an emulator would normally do.
- The Sega 32X was an add-on for the Sega Megadrive which allowed a 32-bit library of games to play on a system that was normally just 16-bit, though it suffered from having its own video output, and its own AC adapter in order to work.
- The Nintendo DS had a secondary cartridge port to act as a dongle for several games.
- USB host connectivity grants more flexibility to computer-based devices
- Older cars that "externalized" their CD players and changers from the head unit can now use "emulators" that allow USB and SD cards with MP3s and other audio files to be recognized as "tracks" to the CD control unit circuitry.
- Adapters that convert miniature implementations of an interface to the full-sized equivalent, or are required to provide the electrical and mechanical interfaces for expansion cards that cannot physically accommodate them (such as PCMCIA, Compact Flash and ExpressCard expansion cards which are just millimetres thick, too small for a standard connector without having the connector and housing extend beyond the dimensions specified by the standard). Although commonly referred to as "dongles", the alternative term "Pig-tail" is favoured by some in the IT industry, due to the appearance of a full-sized connection element, with a short, thin wire extending, somewhat reminiscent of the rear of porcine animals. The term is somewhat descriptive, and allows one to avoid using the word dongle except for its original meaning.