tightening of which trapped the stripped end of the wire in the eye of the split pin to establish a secure connection. The wander plug may have pre-dated the banana plug, but was virtually obsolete by the 1970s, by which time most of the equipment requiring them was long obsolete. Wander plugs generally would not inter-mate successfully with banana sockets and attempts to do so by spreading the brass tip often ended with its fracture. The tip of some banana plugs could be forced into some sockets intended for wander plugs, but would invariably be insecure. Electrical safety Quality banana plugs and cables are typically rated for 30 V at 15 A. Cheaper cables may have one or more downsides: lower quality plugs, smaller diameter wire, lower strand count wire, thinner insulation, lower quality insulation. Unsheathed banana connectors are not usually rated for mains voltage. One reason why banana connectors are not rated for mains usage is that an exposed banana plug or socket can present a shock hazard if connected to an energized source. A plug that is only partially inserted into a jack can also present a risk of accidental contact, because the conductive surface of the plug will not be completely covered. This can especially happen if a 20 mm long plug is inserted into a socket that is only intended for 15 mm long plugs. Some banana plugs have exposed set screws that are electrically connected to the wire. When stacking plugs using transverse holes in a plug, large parts of the pin of the second plug are exposed. Another reason why banana connectors are not rated for mains usage is the lack of double insulation of wires and connectors. The hazards include electric shock, electrocution, burns from accidental short circuits, and damage to the attached equipment. Where electrical safety is an issue, sheathed plugs and sockets are used. These plugs have fixed or sliding sheaths or other devices to protect the user from accidental contact with live conductors, but are still largely compatible with the original design. When inserted, the sheaths of the plug and socket overlap fully, ensuring that no live metal is exposed. A typical design is now required (IEC 61010) on multimeter test leads and several other measurement and laboratory equipment. In this design, the metal banana plug is entirely sheathed in a plastic tube and inserts into a deeply recessed jack