Modified Modular Jack

The Modified Modular Jack, also known as the MMJ connector, or more rarely DEC MMJ, is a small form-factor serial port connector developed by DEC. It uses a modified version of the 6P6C modular connector with the hook displaced to the side so standard modular connectors found on Ethernet cables or phone jacks could not accidentally be plugged in. MMJ connectors are used on Digital minicomputers, such as the PDP-11, VAX and Alpha based machines and to connect terminals, printers or serial console servers.