The industry standard for most EEG and EMG needle electrodes, surface electrodes, and alligator clips is the 1.5mm “touch-proof safety socket.” Such sockets can be plugged into almost any modern EEG, ERG, or EMG machine. Technically, these 1.5 mm touchproof connectors fall under the DIN 42802-1 standard (under IEC 60601-1; sometimes written as DIN 42 802), which was adopted over 20 years ago to make electrodes safer. There are no longer any exposed metal pins; all metal components are recessed within plastic housings to minimize the risk of electrical shock. 1.5mm is the diameter of the recessed metal pin inside the EMG or EEG machine’s receptacle. The actual outer diameters of the plastic electrode plugs (and the corresponding receptacle in your machine) are typically just over 4mm. The recessed pin on the machine is the “male” half of the connection, and the touch-proof safety socket on the electrode is “female,” although it has the appearance of a plastic pin. As can be seen in the picture, touch-proof safety sockets come in wide variety of shapes, colors and appearances, but all are designed to fit in the same receptacle on your EEG or EMG machine.
One big exception is concentric EMG needle electrodes. Because concentric needles have both active and reference electrodes in one needle, a standard touchproof safety socket is not an option. Instead, concentric needle electrodes typically utilize a reusable cable (“needle holder,” such as BIOC-NH for BIONEN concentric needles or SFC cable for Technomed concentric needles) which connects to the needle on one end and has a 5-pin DIN connector on the other end. Each concentric needle manufacturer has their own proprietary cable that typically connects only to their needles, but all are compatible with modern EMG machines which feature a standard 5-pin DIN receptacle for concentric needle electromyography.