Many sound reinforcement loudspeaker systems incorporate protection circuitry, preventing damage from excessive power or operator error. Positive temperature coefficient resistors, specialized current-limiting light bulbs, and circuit-breakers were used alone or in combination to reduce driver failures. During the same period, the professional sound reinforcement industry made the Neutrik Speakon NL4 and NL8 connectors the standard input connectors, replacing 1/4" jacks, XLR connectors, and Cannon multipin connectors which are all limited to a maximum of 15 amps of current. XLR connectors are still the standard input connector on active loudspeaker cabinets.