LK Keylock Switches APEM LK Keylock Switches provide a high level of security with a four-tumbler key barrel. LK series 19mm panel mount key switches serve a variety of commercial applications that require security and restricted access. LK Keylock Switches provide multiple key pull position options and 45° or 90° indexing. This APEM series features a 4A (at 125VAC or 28VDC) or 2A (at 250VAC) contact rating and -30°C to +85°C operating temperature range.