Connector arrangement with staggered mating

An improved electrical connector. The connector includes a first connector having a housing for receiving first contact elements and a slider slidably disposed on the housing for receiving second contact elements; a second connector for receiving first counter contact elements and second counter contact elements; and a retainer which allows displacement of the slider such that the second contact elements secured thereto contact the second counter contact elements only when the first and second connectors are completely connected together by a locking device. During mating the first contact elements and first connector contact elements become fully engaged, but no current flow occurs. At this stage, springs act to move the slider forwardly to cause second contact elements which move with the slider to engage second counter contact elements to switch on current to contact elements and to block release of lock arm.