RJ11/RJ12 – Widely considered to be the “standard” connection, almost all cash drawers will have this fitted by default. It is identical in size and general appearance to the type of connector used on a typical home phone system. RJ11 is the more commonly used term.

A true RJ11 connector has 4 gold contacts, Most cash drawers and receipt printers require at least 5 pins to communicate with each other correctly, Using a 4 pin RJ11 connector could potentially damage your printer or cash drawer.

The RJ11might also be called a Drawer Kick interface or DKD. It might also be referred to as an Epson/Star/Citizen interface as these are the most common brands of receipt printer to which the cash drawer might be connected. However, the RJ11 will work with almost any brand of receipt printer, provided it has an RJ11 socket.

DSUB 9 pin – Similar in appearance to a computer monitor cable with less pins, the DSUB 9 pin interface might also be known as the DB-9 or DE-9. It is actually identical to the serial interfaces which used to come fitted on most computers. Cash drawers fitted with these interfaces can be connected directly to such computers and used in conjunction with specially programmed POS software. It is also possible to buy adapters that will convert the DSUB 9 pin to a more modern computer interface or to a standard RJ11 connection.

2.5mm jack – This is similar to a headphone jack. Very few POS accessories will have a 2.5mm socket for you to plug such a jack into. Instead, these jacks allow you to choose from a range of other interfaces by quickly and easily connecting an adapter.