Allen-Bradley 440K-MT55104 Safety Interlock Switch

The Allen-Bradley Guardmaster MT-GD2 MT55104 tongue interlock switch is a rugged, red die-cast safety device designed to guard access to hazardous equipment. It features two safety contacts (normally closed) and two auxiliary contacts (normally open) with a break-before-make sequencing and a latch-release model type for secure door retention. The MT-GD2 Tongue Interlock uses a 12-pin M23 quick-disconnect connector and, in this variant, includes a 1/2 in NPT adapter for conduit entry. Insulation ratings are Ui 2500 V and Uimp 2500 V, supporting robust electrical isolation in safety circuits, and the unit offers a mechanical life of up to 1,000,000 cycles with an operating temperature range of -20 to +80 °C. Electrical life and load ratings specify 1 mA at 24 V DC for 1,000,000 operations, and with a 2 A fast-acting fuse, about 500,000 cycles for resistive or inductive loads, in line with IEC 60947-4-1 and IEC 60947-5-1. In typical industrial use, this interlock helps prevent machine startup when a guard is open, and it is commonly monitored by safety relays or safety PLCs as part of a guarded protection circuit.