The Modified Modular Jack (MMJ) is a small form-factor

serial port In computing, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel. ...

connector developed by

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...

(DEC). It uses a modified version of the 6P6C

modular connector A modular connector is a type of electrical connector for cords and cables of electronic devices and appliances, such as in computer networking, telecommunication equipment, and audio headsets. Modular connectors were originally developed fo ...

with the latch displaced off-center so standard modular connectors found on

Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...

cables or phone jacks cannot accidentally be plugged in. MMJ connections are used on Digital

minicomputer A minicomputer, or colloquially mini, is a class of smaller general purpose computers that developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, ...

s, such as the

PDP-11 The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of all models were sold, ...

VAX VAX (an acronym for Virtual Address eXtension) is a series of computers featuring a 32-bit instruction set architecture (ISA) and virtual memory that was developed and sold by Digital Equipment Corporation (DEC) in the late 20th century. The V ...

and

Alpha Alpha (uppercase , lowercase ; grc, ἄλφα, ''álpha'', or ell, άλφα, álfa) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter aleph , whic ...

systems, and to connect terminals, printers, and serial

console server A terminal server connects devices with a serial port to a local area network (LAN). Products marketed as terminal servers can be very simple devices that do not offer any security functionality, such as data encryption and user authentication. ...

s.Andrew Oliviero, Bill Woodward ''Cabling: The Complete Guide to Copper and Fiber-Optic Networking'', John Wiley & Sons, 2009, ISBN 470550058, page 295 The MMJ connector has six conductors, using a superset of the

RS-423 RS-423, also known as TIA/EIA-423, is a technical standard originated by the Electronic Industries Alliance that specifies electrical characteristics of a digital signaling circuit. Although it was originally intended as a successor to RS-232C of ...

serial communication standard. The six pins are Tx and Rx for the data transmission, their return paths, and DSR and DTR for handshaking. The transmit and receive signals are differential, i.e. each signal is the voltage difference between the line and its associated ground, as opposed to a voltage on a single connector relative to a common reference. The system can also emulate RS-232 signaling by combining the lower voltage sides of each signal to the RS-232 signal ground line. When connecting two DTE devices such as a computer and a printer, the Digital BC16E

crossover cable A crossover cable connects two devices of the same type, for example DTE-DTE or DCE-DCE, usually connected asymmetrically (DTE-DCE), by a modified cable called a crosslink. Such a distinction between devices was introduced by IBM. The cross ...

is used. Thrustmaster is using the MMJ connector for connecting its line of rudder pedals and racing pedals to either USB via a proprietary Thrustmaster Adapter, or directly to a joystick or racing wheel. The

Lego Mindstorms Lego Mindstorms is a hardware and software structure which develops programmable robots based on Lego building blocks. Each version includes computer Lego bricks, a set of modular sensors and motors, and Lego parts from the Technic line to ...

sets, beginning with the NXT, used similar plugs for motors and sensors to prevent the connection of standard telephone cords.{{cn, date=August 2019

CEA-909 CEA-909 is the ANSI standard for 8VSB/ATSC smart antennas. The basic concept is that the smart antenna either physically rotates toward the signal, or is stationary, but has elements pointed in different directions and uses only those elements that ...

uses the MMJ connector for control signals to a smart antenna, which can either physically or electrically rotate for maximum signal strength.

References

External links

Wiring schemes for Modified Modular Jack cables and converters
Networking hardware

See also

References

External links