The standard diameter of front operation head of board back type, board back cable type built-in explosion-proof component is 30mm. The operation head is installed on the board of 1 up to 6mm thickness.The signal lamp, button and switch module are connect to the pre-installed front operation head part with a clamp. The board back type built-in explosion-proof component is mounted in the increased safety ( Ex-e) enclosure. The degree of protection is up to IP54.The board back cable type built-in explosion-proof component is used for the control apparatus and monitor apparatus widely.The board back type built-in explosion-proof component is connected to terminals. The board back cable type built-in explosion-proof component is connected to the flexible cable of 3m.The built-in ammeter with type of board back, board back cable type is indirect measuring (for current transformer). This measuring way applies to various current ranges. The scales of ammeters for current transformer are interchangeable. All of the scales of ammeters are fitted with adjustable red pointers.