Errorproof device in combination with a modular socket

A modular socket for use with a modular plug, the modular socket comprising:

• a body having a through hole defined in the body for receiving a modular plug and two opposed slots each defined in a side face of the body;
• an errorproof device pivotally received in the body and having two arms respectively extending out to be inserted into a correspondence one of the two slots, each arm having a wedge head formed on a distal end of the arm and an inclined face formed on top of the wedge head relative to a bottom face of the wedge head and a step formed on an inner face of each arm for prevention of an erroneous insertion of the modular plug of a dimension smaller than a distance between the two arms;
• a recovery force providing device securely engaged with the errorproof device to provide a recovery force to the errorproof device when the errorproof device is pivoted;
• and
• a casing securely mounted outside the body to prevent separation of the errorproof device and the recovery force providing device from the body.